I try to keep my promises, and this is what I wrote some time ago:



Regarding a possible mask to be put around the screen, I've been wondering to use some foldable curtains (three, to be exact) and put them above and on both sides of the screen.
I had some "Uhhmm, uhm..." from Patrizia: she's very patient and in love with me, but I have to balance some behaviors... :p
but maybe this could be an effective way to do this in HT room #3...

I recall you we were discussing about the effect of a "average" vs. "bat cave" environment while taking measures.

I've modded my environment, as I said using black curtains (foldable, so I can take both type of data).

I took a projector I've recently received for a review and measured it, with both situations.
Same regulations (default), same screen (1 meter base), same projector's zoom position.
The differences you'll see come out from the ambient.

This is the original setup (same photos I've shown before):


http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06773_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06772_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06774_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06775_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06768_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06781_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06782_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC06784_b.jpg



Next post to see other images... :p

This is the "modded" environment (curtains are black but are closely flashed, so they appear lighter than they actually are):


http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07717_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07718_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07719_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07720_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07722_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07723_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07724_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07725_b.jpg

http://www.htprojectors.com/htprojectors/img/_SHARED/DSC07728_b.jpg

These are the values coming from these two environments.

On the left, "default" conditions coming from the photographs above.

On the right, "bat cave" conditions coming from the photographs below.



http://www.htprojectors.com/htprojectors/img/_SHARED/BC normal Lumens.JPG


http://www.htprojectors.com/htprojectors/img/_SHARED/BC normal CR.JPG

Andrea, nice work. It's interesting to see that the CR is not significantly degraded with a non-bat cave environment. You also used two extremes: all white and all black (ceilings, walls). Wouldn't ANSI contrast be lessened with an all white room?

Wouldn't ANSI contrast be lessened with an all white room?
Correct. As far as light levels and on/off contrast are concerned, it does not matter whether the room is black or white, but ANSI contrast and MTF will be significantly affected. A white room will affect perceived image quality (depth, intrascene contrast, dark detail, etc.) but will not affect the simple measurements Andrea is making. Ambient light (like that sneaking in through a window or from equipment LEDs) WILL affect the black level and on/off contrast measurements though. I would never consider reviewing a projector in a white room, but it certainly is good enough for a few very simple measurements.

The measure was taken with full field 0, 40 and 100 IRE patterns.

I did not make an ANSI CR measure, but a full on/ full off.

Both numbers seem quite similar, though.

I'm confused by this test. Ambient light doesn't affect on/off contrast ratio.

Test ANSI contrast please :)

I'd be interested in seeing the ANSI numbers as well.

Ambient light doesn't affect on/off contrast ratio.
Ambient light DOES affect on/off CR because it can raise the black level if the ambient light level is higher than the projector's black level, in turn affecting the on/off CR.

I don't know about the rest, but that ledge the wheeled chair is next to is kinda scary :D

If you want to really do something interesting, run through the static test patterns linked in the AVS Contrast Thread.
http://www.avsforum.com/avs-vb/showthread.php?t=852467

"It's interesting to see that the CR is not significantly degraded with a non-bat cave environment. "

As was already alluded to, the one thing most affected by the changes, ANSI CR, was not measured.

bat caves improve ANSI contrast over ice caves. In either case not lighting the fire in your cave improves ON:OFF.

Not testing either of these things allows the clueless to continue to think they are getting industry leading contrast in their living room with the kitchen light down the hall on.

Andrea, I didn't know you were a tube o phile, bet you have a decent turntable stashed around there some where?

Thanks for the test. On/off isn't too significant of the difference is it? I wonder what Greg uses when he says modified ansi test to take the room out of the results. The only think I could think of is he's shooting the image down a make shift tunnel of some sort. Good you have the eyeone to test off the screen, no ansi testing with the tri-chromat that I can see.

Please run an ansi test.

bat caves improve ANSI contrast over ice caves. In either case not lighting the fire in your cave improves ON:OFF.

Not testing either of these things allows the clueless to continue to think they are getting industry leading contrast in their living room with the kitchen light down the hall on.


Kras,
This is the funniest quote I have seen in a long time. The sad thing is it is soooooo true. You know I see people on here and in my work that will argue over colors, contrast ratings and the like over a particular PJ like it is life and death. Then I see images of their setup and its in a white or beige room with windows and no light control. I understand that many have limitations on rooms and spouses, etc but they would be just as well off with a old Infocus DC2 design that is a light cannon than the $15K contrast champ. They don't realize they just blew about $10K on no improvement (in their environment). Thankfully it is what keeps many in business though.;)

Hey, stop wasting time posting and get back to reviewing the W20000 ;)

Hey, stop wasting time posting and get back to reviewing the W20000 ;)


Thw W20000 I had was deemed defective and is on its way back to BenQ. I will not get another unit until all the firmware issues are worked out. It will be quite some time before you see anything from me on the W20000. I posted that I was bowing out of the thread but I guess some have missed it. I wish I could delete the thread and may ask the moderators to do so.

I wish I could delete the thread and may ask the moderators to do so.
Just let me know, Eric...;)

Or you can just delete it yourself by going back and deleting your first post.

Thw W20000 I had was deemed defective and is on its way back to BenQ. I will not get another unit until all the firmware issues are worked out. It will be quite some time before you see anything from me on the W20000. I posted that I was bowing out of the thread but I guess some have missed it. I wish I could delete the thread and may ask the moderators to do so.

Nah, I saw that you were waiting to get new firmware, I just felt like giving you a hard time :eek: hence the ;)

Just to recall.
Projector: don't care, same conditions throughout the test
Meter: DeltaOhm DO 9847 with LP471 Phot probe calibrated sensor
Screen dimension: base 1 meter, 16:9
Room temperature: 24.2° - 24.4°C
Sensor temperature: 24.4° - 24.7°C
Pattern: 4 x 4 16:9 checkerboard
ANSI contrast: average white / average black
Units (as reported below): lux



Standard conditions data:


http://www.htprojectors.com/htprojectors/img/_SHARED/CB STD.JPG







Bat cave conditions data:


http://www.htprojectors.com/htprojectors/img/_SHARED/CB BC.JPG





Resulting ANSI contrast ratio values:


http://www.htprojectors.com/htprojectors/img/_SHARED/ANSI CR.JPG



Difference: 14.18%.

Very nice, that is a significant difference, and you only have 1/4th of a bat cave. :)
I don't think the advantage of a bat cave is limited to ANSI contrast however. In a total batcave you watch the movie and can see nothing else. You are no longer in your living room. Playing Mass Effect on the XBox 360 on my 120" screen in my bat cave is just amazing. No numbers can really explain it.
Warren.

Wow, these results reinforce what many people have said: high ANSI CR (>/~ 600:1 as given by good dlp pj's) is RAPIDLY degraded by an imperfect room, much more so than o/f CR (which is largely unaffected by an imperfect room).

This seems to suggest (doesn't it?) that in an imperfect room, one will get the more useful enhancement from pj's with high o/f CR (e.g., the JVC RS1 or 2) than those with less o/f CR but very high ANSI CR (e.g., the best dlp's). Is this a correct interpretation of these results?

Thanks Andrea for taking the time to do this.

Considering you are testing with a projector that is not particularly bright, wouldn't a higher lumen projector such as an RS1/HD1 have a more significant difference in ANSI when comparing a bat cave vs. a room with white walls?

"I think this means BOTH are equally affected by a batcave, for the positive."

No; if the walls were mirrors, on/off CR is the same, because the surfaces' reflectivity changes the on and off values by the same factor.

"Projector: don't care, same conditions throughout the test"

The projector does matter though since its overall brightness and ANSI contrast itself come into play.If you are getting 57:1 at the screen on a projector that has an ANSI contrast of 60:1 your room has a small effect on the ANSI contrast. If you are getting 57:1 at the screen on a projector that is 700:1 ANSI contrast then we know the room is still greatly limiting the ANSI contrast.

Shawn

Curious to see if having a bat cave would make a difference on a projector that has low ANSI like the RS1 (Lcos) compared to a Projector that has a much higher ANSI with DLP Tech. Having a batcave only beneficial for DLP owners?

That's what I was wondering too, Buttabean.

It would appear with the very low ANSI in both setups that you have left your equipment LEDs on in both cases - and they are the determining factor in these results - not the room change.

Either that or you are using some horrible biz projector with the worst possible ANSI such that the room cannot have any influence it is so bad to begin with - also having way more more brightness than an HT PJ is the standard way that biz PJs overcome the room.

I presume you are also measuring the full size screen and not a closeup at the lens. I do the latter when I calibrate so the room has little impact - I used to do the former but customers find it demoralizing...

"Curious to see if having a bat cave would make a difference on a projector that has low ANSI like the RS1 (Lcos) compared to a Projector that has a much higher ANSI with DLP Tech. Having a batcave only beneficial for DLP owners?"

To have even say 300:1 in room ANSI contrast isn't going to be terribly easy. Most rooms will influence the ANSI contrast of a LCOS projector too. I haven't measured my RS-1 for ANSI yet but I will give that a try at some point and see how that changes with the room doing its thing.

On a Sharp 12k I measured a little over 700:1 at the projector and at the screen around 550:1 in my bat cave. (Dark gray carpet, black velvet on the ceiling, black velvet curtains covering all the walls on the front half of the theater, dark red velvet curtains covering all the walls in the back half of the room no equipment other then the RS-1 in room and no windows.)

Also a bat cave has other benefits besides just ANSI contrast. When the lights go down and the only thing you can see is the screen it really draws one into the picture more. Or at least it does for me. I started with flat black painted walls up front and dark red paint in the rear with a black painted ceiling (with acoustic foam on it) and moving to the velvet everywhere was not subtle.

Shawn

"Curious to see if having a bat cave would make a difference on a projector that has low ANSI like the RS1 (Lcos) compared to a Projector that has a much higher ANSI with DLP Tech. Having a batcave only beneficial for DLP owners?"

To have even say 300:1 in room ANSI contrast isn't going to be terribly easy. Most rooms will influence the ANSI contrast of a LCOS projector too. I haven't measured my RS-1 for ANSI yet but I will give that a try at some point and see how that changes with the room doing its thing.

On a Sharp 12k I measured a little over 700:1 at the projector and at the screen around 550:1 in my bat cave. (Dark gray carpet, black velvet on the ceiling, black velvet curtains covering all the walls on the front half of the theater, dark red velvet curtains covering all the walls in the back half of the room no equipment other then the RS-1 in room and no windows.)

Also a bat cave has other benefits besides just ANSI contrast. When the lights go down and the only thing you can see is the screen it really draws one into the picture more. Or at least it does for me. I started with flat black painted walls up front and dark red paint in the rear with a black painted ceiling (with acoustic foam on it) and moving to the velvet everywhere was not subtle.

Shawn

One thing I did notice when I placed the valance above the screen (before was blue then white ceiling) the black floor of the projector no longer looks completely black and you can see a very small amount of brighter corners. If I don't mention it to anyone no one notices the corners.

Does ones eyes adjust the same way to ANSI contrast?

The only LEDs I could think of are the UPS ones, located more than one meter from the screen (not show in the photographs). I took a measure and the reading was 0.00 lux at that distance; the player display was covered for avoiding even stronger interferences.

So this didn't affect the measure.

I'm not getting 57:1 of ANSI from a projector that could have 700:1.
I'm getting 57:1 vs. 50:1, same conditions, bat cave vs. std.

I don't see other situations where this number could raise up to 700.

The projector Andrea is using is the Epson TW2000, which is the best LCD projector today, capable of better than 400:1 ANSI contrast.

If you get 57:1 ANSI contrast in your batcave, then either of the following is true:
1. There is still much white area in your "batcave".
2. Your measurements are flawed, maybe because you pointed the sensor incorrectly, or maybe because of a damaged lumen sensor.

57:1 ANSI contrast is what people get with a 100% white room. This is not a result for a batcave.

The only alternative to what I say, is that the rules of physics somehow do not apply in your room.

Also a bat cave has other benefits besides just ANSI contrast. When the lights go down and the only thing you can see is the screen it really draws one into the picture more.

That's exactly the effect I'm going for! Except that I don't have a dedicated theater to do it in, so I'm trying various tricks in my design to achieve it to some degree in my living room/home theater.

I started with flat black painted walls up front and dark red paint in the rear with a black painted ceiling (with acoustic foam on it) and moving to the velvet everywhere was not subtle.

Shawn

I'm trying to get as close to that as possible, using material wherever possible vs paint to kill reflections.

Right now in my design the walls will be covered with a darker-than-mid-tone fabric wall covering. I plan to have the screen wall painted black (or use black material of some sort), and for killing side reflections I plan on dark brown velvet curtains (black is just too much for a living room), that will, when pulled all the way out, span from the sides of the screen about 9 feet along the side walls toward the viewer.

Will be using a dark brown carpet with a very large black border, so the first 2 1/2 feet out from the screen will be black carpet, then beyond that dark brown.

So that is using dark fabrics to deal with light reflections on all sides except the ceiling. I don't know how much using a darkish (not black) paint on the ceiling will diminish the gains of using fabric on all the other nearby surfaces.
I'm trying to figure out some aesthetically pleasing way of getting fabric on the ceiling up to a few feet out from the screen, but it ain't easy.

As a video/film/HT nut I want to actually get as much of the performance of
a projector possible. Integrating those techy demands into a living environment can be hair-pulling.

The projector Andrea is using is the Epson TW2000, which is the best LCD projector today, capable of better than 400:1 ANSI contrast.

If you get 57:1 ANSI contrast in your batcave, then either of the following is true:
1. There is still much white area in your "batcave".
2. Your measurements are flawed, maybe because you pointed the sensor incorrectly, or maybe because of a damaged lumen sensor.

57:1 ANSI contrast is what people get with a 100% white room. This is not a result for a batcave.

The only alternative to what I say, is that the rules of physics somehow do not apply in your room.

The projector I'm using IS NOT an Epson TW 2000. You saw a photo of an Epson taken two months ago.

Light can't be produced from nothing.
I pointed the sensor to the projector as it should be.
My sensor gives the same response as the other 4 I have, one of them is NIST certified.

What sensor are you using for your measures?
What are your actual results?

"One thing I did notice when I placed the valance above the screen (before was blue then white ceiling) the black floor of the projector no longer looks completely black and you can see a very small amount of brighter corners."

That might be a couple of things there. The first is that you now have a very black reference point near the screen that the screen isn't truely black is just more obvious. Or it could be that reflections from the ceiling were polluting the screen such that it sort of masked the bright corners. Or the reflections off the ceiling might have been raising the level of light hitting your eyes somewhat. You eyes irises might have been closed down a little more in response to that which would reduce your low light level vision. Blocking those reflections with the valence might have made your eyes open up a little more enough that your low light vision improved to the point of being able to see the bright corners. Or maybe something else too.

Shawn

"That's exactly the effect I'm going for! Except that I don't have a dedicated theater to do it in, so I'm trying various tricks in my design to achieve it to some degree in my living room/home theater."

It will be much harder in a living room. I don't know how much flexibility you have in this but one thing that can help with this is sitting closer. The more the screen fills your vision the less of the rest of the room you have to hide... at least when watching the screen.

"I don't know how much using a darkish (not black) paint on the ceiling will diminish the gains of using fabric on all the other nearby surfaces."

It wouldn't be ideal but I highly doubt it would render the gains of the fabric on your side walls and up front pointless. Esp. if your screen is hung down the wall a bit to give some physical space between it and the edge of the ceiling.

"Integrating those techy demands into a living environment can be hair-pulling."

That is for sure. My wife would have shot me if I tried pulling this off upstairs. But in the theater in the basement she loves the look.

Good luck,

Shawn

"One thing I did notice when I placed the valance above the screen (before was blue then white ceiling) the black floor of the projector no longer looks completely black and you can see a very small amount of brighter corners."

That might be a couple of things there. The first is that you now have a very black reference point near the screen that the screen isn't truely black is just more obvious. Or it could be that reflections from the ceiling were polluting the screen such that it sort of masked the bright corners. Or the reflections off the ceiling might have been raising the level of light hitting your eyes somewhat. You eyes irises might have been closed down a little more in response to that which would reduce your low light level vision. Blocking those reflections with the valence might have made your eyes open up a little more enough that your low light vision improved to the point of being able to see the bright corners. Or maybe something else too.

Shawn

I'm thinking combination of the ceiling and the last one you mentioned. The ceiling above the screen is angled about 40 degrees. It's only really noticable when watching 2.35:1 movies since my screen is 16:9. Starting to bug me and might have to open my wallet up for a panamorph uv200 haha. That's for another thread I don't want to get this one off track. Sorry Andrea ;)

As a video/film/HT nut I want to actually get as much of the performance of
a projector possible. Integrating those techy demands into a living environment can be hair-pulling.
Richard,

I commend you for your efforts (I've been thinking about something similar), but don't forget your eyes...
The darker the environment and projected image, the wider your pupils will be...
A couple of years ago, I experimented with a very dark neutral-density filter.
Yes, the image got darker, but then my eyes adjusted to compensate...
I was hoping I could make the side bars/top bars invisible, but no cigar...

The best way to get "blacks" is too blind yourself with a flashlight for a moment and then look at a dark image on a screen. It should be very black...
:-)

Mike

The projector I'm using IS NOT an Epson TW 2000. You saw a photo of an Epson taken two months ago.

Which projector are you measuring then ?

Light can't be produced from nothing.

Not from nothing, from the white boxes.

I pointed the sensor to the projector as it should be.

When measuring the black box of the ANSI Contrast pattern, the sensor might have picked up light from a white box, because the sensor wasn't aligned correctly in relation to the black box.

My sensor gives the same response as the other 4 I have, one of them is NIST certified.

So the sensor isn't damaged. So, either your room is not totally batcave, or you are pointing the sensor incorrectly.

What sensor are you using for your measures?
What are your actual results?

I don't have a sensor.

Like you, I have a set of curtains that make the room 100% batcave when I want. When I put an ANSI contrats checkerboard pattern, I don't even need a sensor, the black boxes are very very bright grey without the curteins (the reflections from the white walls are *killing* those black boxes), and much much darker with the curtains is batcave mode. The difference is HUGE to the eye.

Again, an alternative explanation is that somehow the rules of physics do not apply in your room. Have you checked for paranormal activity ?

"If you get 57:1 ANSI contrast in your batcave, then either of the following is true:
1. There is still much white area in your "batcave"."

Right, the ANSI is determined not by how much of the room is black but by how much is reflective, because it takes so little light to raise the black level of the black squares.

Which projector are you measuring then ?



A 1080 LCD.




When measuring the black box of the ANSI Contrast pattern, the sensor might have picked up light from a white box, because the sensor wasn't aligned correctly in relation to the black box.
So the sensor isn't damaged. So, either your room is not totally batcave, or you are pointing the sensor incorrectly.


The sensor was in the center of the black box, 90° to the surface, each time. As it must be. It's 4 cm. high, and the only spill light it could pick it's what the projector can throw.



I don't have a sensor.
...
When I put an ANSI contrats checkerboard pattern, I don't even need a sensor, the black boxes are very very bright grey without the curteins (the reflections from the white walls are *killing* those black boxes), and much much darker with the curtains is batcave mode. The difference is HUGE to the eye.
...
Again, an alternative explanation is that somehow the rules of physics do not apply in your room. Have you checked for paranormal activity ?

You should buy a sensor. I should have understood this from the fact that you say "lumen meter" while the sensor is a lux meter. That is different.

Buying one and using it will clarify you why they were invented for.
To avoid "eye judgments" like yours that are very often only misinterpretations of a physical phenomenon.

While I'll be investigating on paranormal activity in my room, please take some time to explain which is the rule of physics saying a projector can't have an ANSI contrast of 57:1.
Then go out, buy one sensor, and measure. We'll discuss about your results, not about your apodictic judgments based on your eyes as meter.

We'll discuss about your results, not about your apodictic judgments based on your eyes as meter.
I believe, and Google appears to concur, that this is the first time that excellent word has even been employed in these august forums. Bravo!

While I'll be investigating on paranormal activity in my room, please take some time to explain which is the rule of physics saying a projector can't have an ANSI contrast of 57:1.

It's not a "rule of physics", but more of an observation that 57:1 falls relatively far outside the norm for a 1080p machine, even an LCD, it's about 1/3 of what would normally be expected.

please take some time to explain which is the rule of physics saying a projector can't have an ANSI contrast of 57:1.

There isn't such rule.

The rule that I talked about deals with reflection. When your walls are white, they will reflect light from the screen, back to the screen, washing out the black boxes.

When your walls are black, on the other hand, they will not reflect light from the screen, back to the screen, hence the black boxes will be much darker.

You are not the first one in the world to measure ANSI CR in a batcave, did you know that ?

Many people before you measured this, and *none* of them ever got anything as rediculessly low as 57:1 (with a projector capabale of producing better ANSI CR than this, of course).

You are doing something wrong, there is no avoiding.

And btw, the current crop of 1080p LCD projectors were measured to have MORE than 300:1 ANSI CR (in a batcave, of course).

Andrea,

What sensor are you using?
What is it's "viewing"/measurement cone angle?

Btw., most materials will reflect some light.
This is very clear when you compare black-color fabrics.
Some (e.g., velvet) appear "blacker" than others.

Mike

There isn't such rule.


Thanks. I thought I was missing something. Now I feel better.


You are not the first one in the world to measure ANSI CR in a batcave, did you know that ?

Many people before you measured this, and *none* of them ever got anything as rediculessly low as 57:1 (with a projector capabale of producing better ANSI CR than this, of course).

You are doing something wrong, there is no avoiding.


The fact that you have no familiarity with measuring instruments pops put from the fact that you are assessing something you can't proof by your own experience (that is called a theoretical experience: so you refer someone else's one and define ridiculus what is only a number). You are raging like a bull towards a number (since you thought this should be 300 or so, the higher the better, as always), not asking what is the relevant question: why are these number not so low, but so similar?

Your thoughts appears to be: since I should get (from others, not from your real life experience) 300:1, the sensor is miscalibrated, the owner has ghosts inside the shell, or you are doing something wrong. Period.

You talk about science, but this is a very personal way of interpreting a phenomenon. Something about Inquisition in the middle age: starting from the conclusion, that is apodictically stated as true, we will demonstrate why the sinner is possessed by the devil, your Highness... The benefit of doubt...

Just a simple advice: more practice, less reading. It's more enjoyable...

Andrea,

What sensor are you using?
What is it's "viewing"/measurement cone angle?

Btw., most materials will reflect some light.
This is very clear when you compare black-color fabrics.
Some (e.g., velvet) appear "blacker" than others.


Mike,
the sensor is the LP471 PHOT from DeltaOhm. I tried on the specs to see the reading angle, that I remember something around 2°, that is actually the spec given for the other luminance sensor I have.
I've been using the sensor for quite a long time and never got erratic responses, which I often check with other instruments.

I'm sure that the black curtains I've been using have somehow a small reflectance (surely they're not deep black absorbers), but there's no doubt that the difference between the conditions you see in the photographs is huge.

I have no doubt that dark conditions are far better for an HT experience, that's trivial; but I honestly expected more from the number. I mean, if the standard is X, I would have expected 2X, 3X, not a simple 15% more.

What it really sounds funny is that no one has asked: what about the other parameters? Same thing? Different?

.......not asking what is the relevant question: why are these number not so low, but so similar?
.....

BINGO !! ;) You Got It !! :cool:

It's not a "rule of physics", but more of an observation that 57:1 falls relatively far outside the norm for a 1080p machine, even an LCD, it's about 1/3 of what would normally be expected.

Just to end this: I never mentioned the conditions under whom the measures were taken, and never said the projector was calibrated.

I can increase a CR simply raising the contrast (i.e. white level), or deepening the black (as far as the projector can go).

You don't know (and I don't remember) under which parameters these numbers were read. I've specified only that they were identical before and after I put the curtains.

So the discussion about the absolute number is useless: get a projector and a sensor, and play with it. You'll see how much you can vary this parameter.

Just to end this: I never mentioned the conditions under whom the measures were taken, and never said the projector was calibrated.

I can increase a CR simply raising the contrast (i.e. white level), or deepening the black (as far as the projector can go).

You don't know (and I don't remember) under which parameters these numbers were read. I've specified only that they were identical before and after I put the curtains.

If you would have simply stated the setup you could have avoided 99.9% of this "discussion", but instead you thought it better to be exceedingly vague and cause unnecessary confusion.

So the discussion about the absolute number is useless: get a projector and a sensor, and play with it. You'll see how much you can vary this parameter.

I have a projector and a sensor, but I can't duplicate the conditions without going to great effort as my room is already all but a bat cave. That said, I've measured simultaneous CRs much higher than that (I'm not claiming ANSI as it wasn't ANSI).

I'm still trying to figure what Greg Rodgers means by modified ansi test setup that takes the room out of the equasion.

How about this, the black and white boxes are pretty large and the Eyeone shoots a beam less than the size of a quarter. You make black cardboard boxes the size of the B/W boxes, fix the eyeone just inside the box facing the key spot. This should help at taking the room out of the equasion.

Good one or bad one? lol

If you would have simply stated the setup you could have avoided 99.9% of this "discussion", but instead you thought it better to be exceedingly vague and cause unnecessary confusion.

I don't know if you and I have the same opinion about the term "vague".
Please read the initial posts again (maybe with more attention) and you'll find the room and sensor temperature too. If you think this is vague, that's OK.

What do you think you are seeing when pointing a finger to the moon? Finger or moon?

How about this, the black and white boxes are pretty large and the Eyeone shoots a beam less than the size of a quarter. You make black cardboard boxes the size of the B/W boxes, fix the eyeone just inside the box facing the key spot. This should help at taking the room out of the equasion.

Good one or bad one? lol

Tom,
it's about 2 years or 3 that I don't use the Gretag to take these measures... :rolleyes: the DeltaOhm reads lux, not cd/mq...

Not BTW: lot of tubes here, not only that little one, but some "old" Sonic Frontiers (D/A, pre amp and Power 2...)!

the sensor is the LP471 PHOT from DeltaOhm.Andrea,

Sorry if I missed it, but you have this pointed toward the projector, right? How is it held in place (are you holding it, is it on a tripod, etc.)? Do you think any reflections from the method you use to hold the sensor could affect your readings? When I've used meters that point toward the projector I've been concerned with that and been careful to do things like make sure I am on the screen side of the meter so that light doesn't bounce off me and then straight into the sensor.

In my mostly black velvet room I found that a Minolta LS110 lightmeter I point at the screen would top out around 200:1 for ANSI CR measurements. After much testing I decided that the meter topped out around there as it was getting some light from the white rectangles (even though it is speced to have a small cone for readings). I made a black velvet lined pipe about 18" long that I put over the front of the meter as I pointed it at the screen to make sure that light from the white rectangles didn't throw things off too much and then got around 400:1 ANSI CR from a projector that was I recall was in the 500:1 to 600:1 ANSI CR range (a Sharp 720p single chip DLP, the 11k).

In my off white walled living room I recall getting more like 100:1 from a High Power screen when measuring from close to the projector, and more like 50:1 from off to the side (I believe I've explained before how a high gain position from a high gain screen will tend to help ANSI CR retention to that viewer because they see more gain than the average gain for reflections around the room). The best screen I recall for ANSI CR retention was the Optoma Greywolf, which was both grey and retro-reflective (both help ANSI CR to viewers in higher gain positions), but it has horrible sparklies. My memory is that I could get around 150:1 ANSI CR even in my off white walled room with it, as long as I was in an ideal position (close to the projector). The DNP Supernova should also be good for ANSI CR retention, but I only had a small sample of it to test, and in that case too I found the visible screen texture to be a big negative.

--Darin

Darin,
thanks as always. It's late here and I need to go to bed (just finished calibrating the projector we're talking about... gee, it was hard!) and I'll try to read with the due attention what I've only rapidly gone through now. Maybe this could be a try... Good night (afternoon for you... :p), and thanks again!

Tom,
it's about 2 years or 3 that I don't use the Gretag to take these measures... :rolleyes: the DeltaOhm reads lux, not cd/mq...

Not BTW: lot of tubes here, not only that little one, but some "old" Sonic Frontiers (D/A, pre amp and Power 2...)!

Ah you're using a light meter, never thought you could read correctly with a light meter facing a screen? I always use my light meter towards the projector just for lumens calculations.

S.Frontiers, one I know very well.

"I made a black velvet lined pipe about 18" long that I put over the front of the meter as I pointed it at the screen "

That's similar to the idea I was talking about referring to Greg Rogers term "modified ansi test" It should work best.

This is probably a silly question since I've never owned any measurement devices like this, but I'll take one for the team since I probably won't be the only newb to wonder such a thing.

My question is: why are we measuring ANSI CR by pointing a sensor at the projector? Shouldn't we be measuring ANSI CR at the screen? Isn't it all those reflections "on the screen" that will effect CR?

This is probably a silly question since I've never owned any measurement devices like this, but I'll take one for the team since I probably won't be the only newb to wonder such a thing.

My question is: why are we measuring ANSI CR by pointing a sensor at the projector? Shouldn't we be measuring ANSI CR at the screen? Isn't it all those reflections "on the screen" that will effect CR?

Thanks for asking this - I was wondering too, but didn't ask for fear that it was obvious to everyone else :)

Another question for Andrea: did you hang a black curtain on the rear of the room? I would guess that reflections of the wall directly opposite the screen would have the largest impact.

Andrea,

Your request from me to use a sensor to back up my claims, is similar to a request from me to break the speed barrier of sound in order to provide proof that a sonic boom will be heard. It was already done and proved, so why bother ?

I understand that you disrespect the results of hundreds of people who measured ANSI contrast in a batcave, and never got a result as absurd as you got (both relatively to the white room, and also in absolute terms).

I'm still not sure what are you claiming here:
1. That your LCD projector's inherent ANSI CR tops at 57:1 ?
2. That your white walls absorb light with a 87% efficiency, in relation to your black cloth ?

Such claims can't be serious.

I think that in order to be productive, this debate should change to try and understand where you gone wrong. If we'll have an answer, maybe other beginners could learn from it and avoid it.

One possible option has already been raised, maybe light from the white boxes still gets to your sensor (in a direct path, not reflection) by some reason, and this could skew the results.

The projector Andrea is using is the Epson TW2000, which is the best LCD projector today, capable of better than 400:1 ANSI contrast.

If you get 57:1 ANSI contrast in your batcave, then either of the following is true:
1. There is still much white area in your "batcave".
2. Your measurements are flawed, maybe because you pointed the sensor incorrectly, or maybe because of a damaged lumen sensor.

57:1 ANSI contrast is what people get with a 100% white room. This is not a result for a batcave.

The only alternative to what I say, is that the rules of physics somehow do not apply in your room.


Is it really >400:1? I hadn't seen any ANSI measurements for the Epson yet, that's encouraging...firmly in DLP territory now.

I think you may have something about the rules of physics not applying...Andrea, how close is your light meter to your Flux Capacitor? This could be the culprit in the results...

Andrea,

Sorry if I missed it, but you have this pointed toward the projector, right? How is it held in place (are you holding it, is it on a tripod, etc.)? Do you think any reflections from the method you use to hold the sensor could affect your readings? When I've used meters that point toward the projector I've been concerned with that and been careful to do things like make sure I am on the screen side of the meter so that light doesn't bounce off me and then straight into the sensor.

Darin, I can say no at 90%... I was holding the sensor from the same position with each of the 16 readings, and I had same clothes on to avoid differences. But this could be a variation, somehow. What I'm wondering is the effect: first, 2nd or 3rd order. Please remember that I "tried" to measure the effect of the UPS LEDs, and I saw 0.00 on the display...


In my mostly black velvet room I found that a Minolta LS110 lightmeter I point at the screen would top out around 200:1 for ANSI CR measurements. After much testing I decided that the meter topped out around there as it was getting some light from the white rectangles (even though it is speced to have a small cone for readings). I made a black velvet lined pipe about 18" long that I put over the front of the meter as I pointed it at the screen to make sure that light from the white rectangles didn't throw things off too much and then got around 400:1 ANSI CR from a projector that was I recall was in the 500:1 to 600:1 ANSI CR range (a Sharp 720p single chip DLP, the 11k).

This is a good idea. Even though I think that the sensor should have a small angle, maybe this could help. I'll try to do something like this and see what happens.

But, once again: I know you are a big CR fan (that I'm not...), but my original question remains: since conditions were the same, why the difference is so small? Not the absolute number, but the difference between the two readings.

If the a possible error could exist, the same error should appear on both numbers.

If a bat cave should produce higher CR numbers, why they are not here?

Any other similar example?

"but my original question remains: since conditions were the same, why the difference is so small? Not the absolute number, but the difference between the two readings.

If the a possible error could exist, the same error should appear on both numbers.

If a bat cave should produce higher CR numbers, why they are not here?"

That point got through, the difference wasn't a huge percentage which I think would probably stay the same no matter how you alter the tests.

This is probably a silly question since I've never owned any measurement devices like this, but I'll take one for the team since I probably won't be the only newb to wonder such a thing.

My question is: why are we measuring ANSI CR by pointing a sensor at the projector? Shouldn't we be measuring ANSI CR at the screen? Isn't it all those reflections "on the screen" that will effect CR?


This is for Tom, too...
One has to choose the instruments and get acquainted with them.
If you want to measure an ANSI CB pointing at the screen, you are making a luminance reading (cd/mq). Since you are aiming to a small box from a distance, your sensor must be highly directive. My Gretag has a 6° angle but not a clear viewfinder, like the Minolta Darin uses instead has.
I have a Photo Research to do this, but I prefer the DeltaOhm reading, that is surely precise since it's positioned inside the box (no error in pointing it).
Once you have a confirmed reading, the CR could be expressed both coming from lux or cd/mq, it's only a ratio.

Reflections on the screen are interactive with each other: this is why the CB was made for, to simulate a real life condition.
I'm not an optic expert, but I recall something called MTF (I guess it was Modulation Tranfer Function), that, if my remembering is right, was the number to express optical "distorsions" in terms of interaction of the lenses when grouped inside the lens.
This should appear on the screen, and measuring on the screen should take this into account.


Another question for Andrea: did you hang a black curtain on the rear of the room? I would guess that reflections of the wall directly opposite the screen would have the largest impact.

The position of the projector is at the opposite side of the screen, and there's only a small part of wall left unobstructed. Since this is the same direction where the light comes from, I think it can be disregarded on first approximation. Once you have covered the 3 main surfaces where the light might come out, I think you are dealing with 2nd and 3rd effect. If not so, I should see a HUGE difference when comparing normal vs. bat cave...

"If a bat cave should produce higher CR numbers, why they are not here?"

Lot of possibilities.

A) Projector doesn't have very good ansi contrast.

B) Meter doesn't have enough low light sensitivity.

C) Meter positioning/angling is changing between readings. If you are hand holding your meter you need to use a tripod. Measure the black/white for each square one square at a time so the meter position is identical for both readings. Use the projectors invert control to switch from white to dark.

D) Too much light polution in room raising the black level measurements. With the projector off is your room dead black so that you can't see your hand in front of your face even after sitting in the dark for a few minutes?

E) Don't really have a bat cave. What material is in those 'arches' near the back of the room? That last picture in your first post shows a light of light reflecting off of that.

Shawn

Is it really >400:1? I hadn't seen any ANSI measurements for the Epson yet, that's encouraging...firmly in DLP territory now.

I think you may have something about the rules of physics not applying...Andrea, how close is your light meter to your Flux Capacitor? This could be the culprit in the results...

You mean the UPS? More than 1.5 meters... I think it should fry my brain if capable of altering a reading... and maybe this had happened! :p

Regarding DLPs... I'm on your side!

Darin, I can say no at 90%... I was holding the sensor from the same position with each of the 16 readings, and I had same clothes on to avoid differences.Holding it in the same place doesn't mean it couldn't cause problems, since reflections getting into the sensor would ruin the results in each case. I'm not saying this was a problem, just that holding it from the same position doesn't mean it wasn't. Extra reflections wouldn't change the white readings hardly at all, but would ruin the black level readings.
This is a good idea. Even though I think that the sensor should have a small angle, maybe this could help. I'll try to do something like this and see what happens.The sensor I'm using is one that I can look through and with the black velvet pipe I can make sure that things are positioned correctly by sight. Even then I have to try to hold things steady there and not waver to where the sensor is reading off the velvet instead of off the screen. With other sensors that you can't look through for where they are pointed the pipe would be harder to use correctly.

Also, as somebody pointed out, you really should be measuring off the screen if you want to know how the room is affecting ANSI CR in the images.

What color is your back wall (or is it covered with dark material)? That one can be pretty important.
But, once again: I know you are a big CR fan (that I'm not...),I have to ask. Since we had that conversation years ago when many projectors were less than 2000:1 on/off CR and you were arguing against on/off CR mattering, have you seen the improvement that the JVC RS2 provides in many dark images with its much higher on/off CR?
... but my original question remains: since conditions were the same, why the difference is so small?I think it could be some kind of measurement error, like something from pointing at the projector instead of at the screen. Picking up light reflecting off the projector from a small angle away from the path to the projector lens, etc. You may need a different sensor for pointing at the screen though.

If your sensor only has a small angle that it reads from then how do you makes sure it is pointed right at the lens and not just reading off the back wall, a different part of the projector, etc.? I don't see how pointing directly at the lens could work for ANSI CR, since lenses have loss in reflections and so I would expect the sensor to pick up light from the white rectangles as they hit the last lens in a way that doesn't indicate the ANSI CR coming off the screen. If there is any dust on the lens that it would probably light up too. If you look at the lens and can see the checkerboard pattern coming out of the last lens element, then the sensor would probably pick that up to if you pointed at the projector.
If the a possible error could exist, the same error should appear on both numbers.Your numbers don't indicate that it doesn't. As an example, let's say the real numbers were 400:1 and 100:1. If an error was introduced that raised the measured black level and took the 100:1 down to 50:1, it would take the 400:1 down to about 80:1.
If a bat cave should produce higher CR numbers, why they are not here?My guesses are measurement error, the projector doesn't have high ANSI CR itself, or the room isn't really a bat cave (I didn't see an answer where somebody asked you earlier about the back wall). I saw you mention the projector is an LCD, but if there is a reason you don't want to give the model number (like it isn't out yet), then maybe you could start with a projector that is known to have high ANSI CR and where you could tell us the model number.

Also, if you want to try taking the room out of the equation and just measure the projector, covering the screen with dark material helps. I've even cut a hole in some dark material so that I can move the hole to the spot on the screen I want to measure and have the dark material covering the rest of the screen (minimizing the amount of light that gets reflected back into the room).

--Darin

Hi Darin,

With my light meter (in lux not fc mode), I found that holding it against the screen facing the pj for ANSI measurements still gave good results (black readings were high enough to be useful IMHO with X.XX readings). Initial results were around 75:1 and final results after modifying a few things in the room were around 200:1. I also found that by covering 80% of the screen with black felt I could read around 400:1 IIRC. Would you say that methodology was flawed since I was reading facing the pj rather than the screen? For on/off I measure from around 2 to 3 feet away from the pj facing the pj.

Gary

I saw you mention the projector is an LCD, but if there is a reason you don't want to give the model number (like it isn't out yet)

It can't be a "soon to be released" projector. There won't be any new LCD projectors before Cedia 2008, a long time from now.

If he has ANY 1080p LCD projector that is sold today (Mits HC6000, Epson TW2000, Sanyo Z2000 or Panasonic AE2000), they were all been meaured for ANSI CR, and all surpass 300:1.

With my light meter (in lux not fc mode), I found that holding it against the screen facing the pj for ANSI measurements still gave good results (black readings were high enough to be useful IMHO with X.XX readings). Initial results were around 75:1 and final results after modifying a few things in the room were around 200:1. I also found that by covering 80% of the screen with black felt I could read around 400:1 IIRC. Would you say that methodology was flawed since I was reading facing the pj rather than the screen?I think it gave you a good idea of how your changes were affecting things and what the projector ANSI CR was, but didn't take your screen gain into account (or gray layer for helping ANSI CR retention, if you have a gray screen). Also, not sure if any reflections off you affected anything, but it sounds like not with your 400:1 measurement. I've also measured with a meter at about screen level, but hold the meter out a little bit from the screen so that I am on the screen side of it. This meter is one that isn't real directional, where it sounded like Andrea's might be very directional (just measures from a small cone, like a few degrees). With one that is measuring a small cone it seems to me that measuring toward the projector would be a problem, since the meter is just measuring whatever that cone is pointed toward (the back wall, a small part of the projector, the projector lens, etc.). I could be wrong about Andrea's meter for this being very directional though.

As far as guitarman's question about Greg's modified ANSI CR, I'm not positive about the whole thing, but I think that Greg only populates the 2 white rectangles near the center of the screen, instead of all 8 white rectangles for the whole ANSI CR test. That way there are less reflections around the room. A person holding a meter to measure one of the rectangles wouldn't be standing where one of the other white rectangles was reflecting off of them also, and same kind of thing for a tripod with the sensor on top of it and pointed back toward the projector.

--Darin

Guys,
thanks for your cooperation, and I guess I'll stop here because I don't want to become repetitive and have some deadlines for coming articles to fulfill.
There are a lot of suggestions to be taken, some of then are really interesting to my eyes, some of them less, but this demonstrates that this matter appears to be capable of fun.

I'd like to summarize here some possible solutions you suggested for an "uncommon event" like two readings being quite similar and different from what was expected.

i) The sensor is broken or has erratic response
ii) The sensor wasn't in the right place and the reading wasn't taken as supposed
iii) A projector must have higher ANSI CR
iv) The room is not a bat cave
v) White boxes alter black boxes so the reading is useless
vi) A strong magnetic field is destroying the sensor's accuracy
vii) The aliens have landed and we are surrounded
viii) Call an exorcist, you're lost!

:p

I still remember I was taught in my first years of engineering studies (even it was a long ago) that 2nd and 3rd order effect from an engineer's point of view can be disregarded, and I think this applies here too. If you'll measure the extension of the black curtains compared to the wall surface you'd see that this might be considered as very small.

Anyhow, I've pointed out many times that the result I was expecting (like all of you, I guess) from this kind of measure should have had a big distance from normal vs. bat cave.
The general rule here says "Ambient conditions will not affect on/off CRr, but it will affect, heavily, ANSI on/off". I don't know who said this for the first time and how he demonstrated this statement, but my answer is simple.

Given that the conditions I've used were not a complete bat cave (but I'd like to see how many 100% real black rooms (I mean with EVERYTHING painted with non reflective paint) are around (and how many happy wifes you'll see as a consequence); given that I've only measured one projector and this is not statistics; given that everything can be improved;

I think that it appears from this experiment that ANSI CR is not heavily altered by room conditions.

I don't know how many among you have tried the same thing (same environment, covering everything with black and make two different measures), that is what I've asked so far.
It seems to me that no one among the persons who wrote here has ever done this: I don't know if others had, and maybe we should ask to the person who stated that a huge difference exists if he ever actually took this measure. And where are the results, that I'd be curious to see.

As I said elsewhere, sometimes I get the feeling that writing here and being non-US puts me in the position that:
a) I'm wrong by definition;
b) my instruments are faulty;
c) what I get, if different from other's result, is useless;
d) if anything of the above applies, go to point a) :p

I tried every time to put numbers and photographs to show the actual environments where the measures were taken and discuss real things. I wonder: how many of the US gurus do the same, how much you really know about the ambient, conditions, tools and accuracy they use? I have no fear in sowing real things, even though this can be origin for discussions, but it's surely fun and gives me the chance to learn (e.g., the bat cave was originated here, and I think it was worth the effort).
Do you have the same direct knowledge of how the work you consider as sacred is handled? :rolleyes:

Let me give a personal response to Darin (we've been discussing for years about CR, and no one will ever chance his mind... :D, but you're great and affordable, Darin, you know I sincerely think this and I still remember our conversation in Vegas): no, I don't think that the main reason for the JVC being a good projector is that it has a better CR. The reason lies in black level, gamma linearity, good colors and spectral response, and excellent low levels performance...
And to Jones too: absolutely no hard feelings at all, this is only a discussion about useless things that are toys. Things that matter are elsewhere, reasons to get angry too!
For those interested, the projector is a ViewSonic Pro8100, though...

http://www.htprojectors.com/htprojectors/img/_SHARED/AVS/DSC08331_b.jpg

Thanks to everyone!

This is for Tom, too...
One has to choose the instruments and get acquainted with them.
If you want to measure an ANSI CB pointing at the screen, you are making a luminance reading (cd/mq). Since you are aiming to a small box from a distance, your sensor must be highly directive. My Gretag has a 6° angle but not a clear viewfinder, like the Minolta Darin uses instead has.
I have a Photo Research to do this, but I prefer the DeltaOhm reading, that is surely precise since it's positioned inside the box (no error in pointing it).
Once you have a confirmed reading, the CR could be expressed both coming from lux or cd/mq, it's only a ratio.

Reflections on the screen are interactive with each other: this is why the CB was made for, to simulate a real life condition.
I'm not an optic expert, but I recall something called MTF (I guess it was Modulation Tranfer Function), that, if my remembering is right, was the number to express optical "distorsions" in terms of interaction of the lenses when grouped inside the lens.
This should appear on the screen, and measuring on the screen should take this into account.



The position of the projector is at the opposite side of the screen, and there's only a small part of wall left unobstructed. Since this is the same direction where the light comes from, I think it can be disregarded on first approximation. Once you have covered the 3 main surfaces where the light might come out, I think you are dealing with 2nd and 3rd effect. If not so, I should see a HUGE difference when comparing normal vs. bat cave...

Before I respond, I want to make it clear that I have zero emotional stake in this. In fact, I'd like what you're saying to be true because it would give me a lot more room color choices for my home theater! :-)

But your answer seems like techno-evasion to me. That's where you throw out a bunch of terms that your intended audience has no way to understand as a way to prove your point, hoping your audience will be too ashamed to admit he has no idea what you're talking about so you can avoid giving an answer in plain english.

Note: I'm not saying that's what you're doing, only that your answer fits the profile, whether intentionally or not. Especially since I revealed myself as a "newb" to this sort of thing several posts up.

Above, Darin mentioned that you'd have been better off reading from the screen. Could you explain in plain english (pretend I'm in 5th grade) why this is not required to get an accurate on-screen ANSI measurement?

I do wonder what the readings would have been if Darin had taken them with his instruments in the same room, measuring off the screen...

Just to make things clear: have I ever wrote that a bat cave or a normal environment give the same results?

Can you tell me where?

I don't think this is techno-whatever: it's plain English, that you should understand much more than me.

No one has asked how much other parameters vary (like color balance, gamma or else): I wrote this before. Maybe you missed it.

I only said that ANSI contrast has a slight variation, not that the ambient has no importance on this.

I don't think that what I wrote here is different from what Darin and others have done: why do you address the question only to me? maybe point d) of my previous post...

A simple answer to your question, though: Darin uses method A (off) , I use method B (on). Which one is better? Who knows? Everything has pros and cons...

Guys,
thanks for your cooperation, and I guess I'll stop here because I don't want to become repetitive and have some deadlines for coming articles to fulfill.
There are a lot of suggestions to be taken, some of then are really interesting to my eyes, some of them less, but this demonstrates that this matter appears to be capable of fun.

I want to say I at least, maybe many others, would like to see your results if you look at some of the comments brought up.

I still remember I was taught in my first years of engineering studies (even it was a long ago) that 2nd and 3rd order effect from an engineer's point of view can be disregarded, and I think this applies here too. If you'll measure the extension of the black curtains compared to the wall surface you'd see that this might be considered as very small.

I agree, I think the changes you made to your room are sufficient to illustrate the difference between "bat cave" and "normal".

Anyhow, I've pointed out many times that the result I was expecting (like all of you, I guess) from this kind of measure should have had a big distance from normal vs. bat cave.
The general rule here says "Ambient conditions will not affect on/off CRr, but it will affect, heavily, ANSI on/off". I don't know who said this for the first time and how he demonstrated this statement, but my answer is simple.

I think another engineering principal is to not take surprising results at face value. They can happen of course, but quite often there's a very good reason results seem odd, and usually, that reason is not that "they're odd".

Given that the conditions I've used were not a complete bat cave (but I'd like to see how many 100% real black rooms (I mean with EVERYTHING painted with non reflective paint) are around (and how many happy wifes you'll see as a consequence); given that I've only measured one projector and this is not statistics; given that everything can be improved;

I think that it appears from this experiment that ANSI CR is not heavily altered by room conditions.

The numbers you posted do suggest that, however science, experience, nor logic concur. Eric Garci has a great calculator on his webpage:
http://home1.gte.net/res18h39/intrascene.htm

If you look there, you can try some things out, like a 250:1 ANSI projector with 0 "room gain", and say 10%. For example a projector with 250:1 ANSI in a "bat cave" (0% room gain) would have an ANSI CR of only 112:1 in a room with 1% room gain.

If we assume your new 1080p LCD has an ANSI CR of 250:1 (reasonable guess) the room gain between "normal" and "bat cave" configurations changed less than 0.5%, you need over 3.5% room gain to get an ANSI measurement of ~50:1. The surprising thing is the minuscule change in room gain despite your drastic changes to the room.

I don't know how many among you have tried the same thing (same environment, covering everything with black and make two different measures), that is what I've asked so far.

I'd really like to, but my room is already dark, and I don't have the means to "undo" that.

It seems to me that no one among the persons who wrote here has ever done this: I don't know if others had, and maybe we should ask to the person who stated that a huge difference exists if he ever actually took this measure. And where are the results, that I'd be curious to see.

I've done measurements in my HT, and I've not seen simultaneous CR numbers as abysmally low as yours, that's really the crux of the problem, no one here can really imagine a 1080p projector with 50:1 ANSI CR.

I really think Darin is on to something, you've got a highly directional sensor and are pointing it at the projector, it's very likely that you're measuring the light off the back windows and not the projector.

As I said elsewhere, sometimes I get the feeling that writing here and being non-US puts me in the position that:
a) I'm wrong by definition;

I don't think that's the case at all. Though I will give you that often times on the forum there's a communication gap (probably due to language) that makes it hard to communicate well with folks in other geographic areas. But really I think the vast majority here are more mature than that.

b) my instruments are faulty;

The questioning of your measurements has nothing to do with you, it has to do with your measurements. A number of us here have done measurements ourselves and the numbers are just shockingly low. Now the projector could really be that bad, and frankly if it were that bad, I wouldn't expect the room to make much difference, but the assumption is that a 1080p projector should be much better than 50:1. And I'm sorry about my vague comment earlier, it was over the top, but this is really what I was getting at, you say the projector doesn't matter, and really it shouldn't, but since we don't know the projector or we can only assume it's "theoretical" performance should be close to that of other models, and your numbers don't jive with that assumption.

c) what I get, if different from other's result, is useless;

Not useless, but not terribly useful until we understand the reason for the apparent discrepancy between measurements and expectations?

d) if anything of the above applies, go to point a) :p

I suppose that is always an option :D

I tried every time to put numbers and photographs to show the actual environments where the measures were taken and discuss real things. I wonder: how many of the US gurus do the same, how much you really know about the ambient, conditions, tools and accuracy they use?

Another part of the problem, and I'll just throw this out there, is that you seem unwilling, unable to acknowledge that something might be amiss with your numbers. When challenged, you throw out the specs of your measurement equipment (which surely is up to the task), point to pictures of your room (which I agree, should do the trick), and finally fall back to just claiming we don't know what we're talking about.

I have no fear in sowing real things, even though this can be origin for discussions, but it's surely fun and gives me the chance to learn (e.g., the bat cave was originated here, and I think it was worth the effort).
Do you have the same direct knowledge of how the work you consider as sacred is handled? :rolleyes:

I personally don't have as much as I'd like, but I've got enough for your numbers to trigger my spider-sense :cool:

"It seems to me that no one among the persons who wrote here has ever done this:"

Quick and dirty but using one of the contrast patterns in my Lumagen (2x2 squares basically) and leaving my ISCO II and ND filters in place I measured about 112:1 contrast (using the projectors vertical invert to switch from white to black) as is. I then covered just the wall nearest the screen (side I was measuring from) with a white blanket from the screen to about 5' out on the wall and measured 79:1. This is with the room still being a bat cave. That is a little more then a 30% loss of contrast from that small amount of white on the wall near the screen.

Shawn

The general rule here says "Ambient conditions will not affect on/off CRr, but it will affect, heavily, ANSI on/off". I don't know who said this for the first time and how he demonstrated this statement, but my answer is simple.

Given that the conditions I've used were not a complete bat cave (but I'd like to see how many 100% real black rooms (I mean with EVERYTHING painted with non reflective paint) are around (and how many happy wifes you'll see as a consequence); given that I've only measured one projector and this is not statistics; given that everything can be improved;

I think that it appears from this experiment that ANSI CR is not heavily altered by room conditions.If you did the actual ANSI CR test and came to that conclusion then it would mean more to me, but based on the fact that many of us have done testing that says otherwise and logic says that reflections of even 2% coming back to the black rectangles would kill that ANSI CR from a high ANSI CR projector, I wouldn't jump to your conclusion. The actual ANSI CR test calls for measuring off the screen. We know that many projectors have ANSI CRs that are higher than 300:1 from the projector, so if you get something way less than that with one of those projectors, there is either something in your environment causing that, or your measurements are wrong. Put another way, if you measured 57:1 ANSI CR in a completely black room, it wouldn't mean that a black room doesn't help with high ANSI CR projectors because more likely explanations are that the projector you are using doesn't have high ANSI CR, the measurements are incorrect, or there is something else in your environment causing the drop from what the projector can do.

Please look at this logically. Without other lighting (including light coming out the back of the projector) a white room cannot hurt the on/off CR (other than very minor effects that I'm not going to go into now). This is from what we learned in school. Basically 1.2x/1.2y is the same as x/y. If the room reflection the same percentage of video white as for video black, it doesn't change the ratios between those for on/off CR with full field images. The same rule doesn't apply to ANSI CR because the reflections around the room light up the dark rectangles a much higher percentage than the white rectangles.

For ANSI CR, a projector with 400:1 ANSI CR has "black" rectangles that are just .25% the level of the white rectangles. So, reflections even raising the darker ones by 1% of the white ones would bring the ANSI CR down significantly (since 1% of the white ones is higher than the projector is putting into the darker ones).
Let me give a personal response to Darin (we've been discussing for years about CR, and no one will ever chance his mind... :D, but you're great and affordable, Darin, you know I sincerely think this and I still remember our conversation in Vegas): no, I don't think that the main reason for the JVC being a good projector is that it has a better CR. The reason lies in black level, gamma linearity, good colors and spectral response, and excellent low levels performance...I didn't really ask if it was the "main reason" :), but 2 of the 3 things you mentioned are related to on/off CR. For instance, "black level". Couldn't be ANSI because those 2000:1 on/off CR single chip DLPs probably had better ANSI CR than the RS2. And the absolute black level is by definition the white level divided by the on/off CR. The good absolute black level of the RS2 even when setup to a reasonable white level is definitely from the on/off CR. And "excellent low levels performance" is also related to on/off CR. A raised black floor (which on/off CR indicates best) affects the low level performance. The ability to use a 2.4 or 2.5 gamma while having things look good is also affected by having a high on/off CR. The RS2 with the same ANSI CR, colors, gamma, etc., except with 2k:1 on/off CR instead of more like 20k+ would not be the same projector as far as the quality of the images in a proper environment.

--Darin

Andrea, I think you and I probably do have a language barrier or something, since now I have absolutely no idea what you're talking about. Several of the things you said in that last post (your response to me) really seemed to come out of left field. I guess I'll digress and go back to watching from the sidelines.

I think that it appears from this experiment that ANSI CR is not heavily altered by room conditions.I wanted to add some more about this claim.

Just from simple physics we know that if there were no reflections from the room or anything in the room (other than the screen), the ANSI CR off the screen would be the same as the ANSI CR from the projector. Hopefully people can agree with that one (or only disagree because of very small effect s , like color balance, which we can ignore because they are basically like rounding error).

Does anybody (including Andrea) disagree with any of these:

1. There are multiple projectors with ANSI CRs over 400:1.
2. The only way the off the screen ANSI CR with one of those projectors would be less than 400:1 would be because of other lighting in the room, reflections from the room or things in the room, or measurement error.
3. We don't know the ANSI CR for the projector Andrea used for this test.
4. If the projector in the test has an ANSI CR of 300:1 or more, then the only ways for Andrea to measure under 60:1 are reflections, other lighting, or measurement error.

Not sure if any of this is making sense, but if Andrea had taken a projector with 400:1 ANSI CR and measured >300:1 ANSI CR in both a blacked out room and a white room then the argument could be made that the room didn't really matter. But measuring under 60:1 means that the projectors ANSI CR is lower (in which case the test doesn't tell us what happens with a high ANSI CR projector), the room is still killing the ANSI CR after some modification to the room (but not all the way to a black hole), or measurement error. So, if there is no measurement error and the projector has high ANSI CR, this just means that the room needs to be made better and possibly a screen that is good at retaining ANSI CR should be used (measurements would of course have to be taken off the screen to gauge this effect).

In order to claim that the tests done prove that ANSI CR is not heavily altered by the room conditions a person would have to say that the ANSI CR of this projector was low to begin with, or that the ANSI CR was heavily altered by the room, but just a similar amount for both sets of measurements. But far from what a theoretically perfect room would do (since a theoretically perfect room wouldn't decrease the ANSI CR at all). And I think enough of us have done measurements that show there are rooms capable of retaining well over 200:1 ANSI CR off the screen (which is a long ways from the 57:1 measured here). So, if there are no measurement errors, then this particular room must be killing the ANSI CR by a lot in both configurations (or there was never high ANSI CR from the projector to begin with).

I'm personally guessing measurement error. Covering the screen with black material and then redoing the test should narrow it down, since the reflections around the room would have to be reduced significantly by killing most of the light coming off the screen. If the measurement is still in the 60:1 range or so that way, then I would say measurement error or that the projector has low ANSI CR itself. If the ANSI CR measurement went way up after covering the screen with black material, then I would say that room reflections even with the darker configuration would be the likely culprit here.

I hope that makes at least a little bit of sense. :)

--Darin

I'm considering going external from the house, on the parking pad next to my garage for my 'Batcave'. Perhaps a gutted 'Airstream' trailer, painted flat black inside, or a shipping container. Gotta have enough room for my eight foot wide screen & must have wife/baby/neighbor type soundproofing.

Would love to build/construct my own 'Batcave' but this necessitates building permits, which are a HUGE hassle in my city. The quest goes on...

How does it look like with movies? ;)

You have had the Epson in the same room with the same screen I gather. How does this projector compare to the Epson?

Andreas

despite several people claiming in this thread they have measured a magnitude difference between white and black caves ANSI on screen contrast- you dismiss it and say you don't know of anyone else making these measures- therefore your measurement must be right?

It is rather obvious to anyone that if you measure the PJ lens at the screen using an instrument with a 2 degree visualization window - that it is impossible to see a black or white square in isolation. Do a little trig and prove to the contrary yourself. Just because the pod at the screen is in a black square - does not mean the 2 degree window at the lens is in a black square.

12' * sin(2d) = 0.4' window.

If it is truly a light meter that is not reading a surface - but reads the incoming light - what is its focal point for light it sees. How do you know the sensor cannot "see" the incoming white squares in its peripheral vision?

Please redo this experiment taking darins advice - use a sensor reading the screen directly with a tube to avoid light contamination on the sensor that is not falling on the screen. You do everyone a disservice by forming a conclusion such as bat caves do not improve ANSI contrast when others more capable at measuring things have clearly proven the opposite is true.

The on/off measurements he had for the RS-1/2 were in the 4-5k:1 range. This would suggest to me that, barring measurement error, there is ambient light in the room which could be affecting the measurements.

I read most of the thread, but somehow it did not register that the sensor was pointed at the projector!
One of the photos appears to have the probe pointed at the screen (maybe not...).

I think, Kras hit the nail in the head!
If pointed at the projector, the sensor must pickup light outside of the (screen) area being measured.
The light that strikes the screen is not parallel. It is a large cone with the top, bottom, and sides "chopped off."

I am also curious how the measurement would come out with the suggested method.
Btw., artificially narrowing a measurement angle with a tube would alter (lower) the absolute values,
but the ratio of values should not be affected, I think...

Mike