AVS › AVS Forum › Display Devices › Digital Hi-End Projectors - $3,000+ USD MSRP › Max acceptable fL for black ?
New Posts  All Forums:Forum Nav:

Max acceptable fL for black ?

post #1 of 54
10/4/09 at 5:47pm
Thread Starter 
I am trying to determine what a acceptable range for the maximum level of black is.

So im talking about 0 IRE, full screen, black.

There is obviously going to be personal preference and tolerance, but what are really ideal numbers for real life installations. Yes I know 0 fL is perfect, but this is not what i want to know. For example what is your black level in fL ?

At what point is it too high ? In fL ?
Reply
Reply

AVS Top Picks

post #2 of 54
10/4/09 at 6:16pm
Most people lack the ability to really accurately measure this since it requires a certain type of spot light meter, and it has to be one with an ability to read accurately at fairly low black levels. We are talking tenths of a foot Lambert. You could measure with some colorometers too, but again, most people don't have these, and even those of us who do don't necessarily have one that is going to give the most accurate number at those low levels.

I have both a colorometer from eye one and a spot type light meter from Sekonic. The Sekonic is a bit more accurate at measuring black levels, and I find I get different numbers quite frequently, so I've begun using an averaging method of not only a series of spot readings, but done at different times. I have been using a matte white unity gain screen, and with that my Sony VPL-VW40 measures around .0015 or so, which is beyond the resolution of my scope, but the number tends to go back and forth between .001 and .002. However, I've recently upgraded to the SI Black Diamond 2 .8 gain screen, and this has dropped my black levels quite noticeably. No idea exactly how much since I was already at the limit of my measurement system.

I think a lot of people would argue that absolute black levels aren't really all that important, especially since projectors like mine will produce very low black level numbers, but still lack the dynamic range, even in dark images like star fields, that something like the JVC models might.

Some feel that as long as their is enough range between the blacks and whites, that the eye will be fooled into seeing excellent blacks. I don't happen to buy this, with many of my favorite types of movies, a lack of really inky blacks distracts me. I like the blackest blacks I can get, and I'm yet to see a setup that offers what I would consider ideal. Even the astounding blacks of the very best projectors today produce an image where all black portions of a scene looks a few shades brighter than black, so I'm still waiting.

So to directly answer your question, how low is low enough. I suppose for me it would be 0.0000000000 fl, but given that this is impossible, I consider .001 a really good number, and anything below that an even better number. I also feel it's important to choose screen sizes so that you are able to get at least 12 fl with a 100ire image, and really more is better here. I mean, I could paint my wall black and get the deepest darkest blacks I could possibly want, but the whites will be far too low.
Reply
Reply
post #3 of 54
10/4/09 at 6:39pm
Quote:
Originally Posted by xymox View Post

I am trying to determine what a acceptable range for the maximum level of black is.

So im talking about 0 IRE, full screen, black.

There is obviously going to be personal preference and tolerance, but what are really ideal numbers for real life installations. Yes I know 0 fL is perfect, but this is not what i want to know. For example what is your black level in fL ?

At what point is it too high ? In fL ?

Chris, I don't think this is really that meaningful a question. For instance, you can have the same display with the same on/off CR on two different sized screens which give you VASTLY different absolute black levels (and white levels) but completely identical on/off CR.

This is why CR is the metric that is more useful than a measurement of absolute black level which doesn't really tell you anything very meaningful by itself.

What matters is what the black levels appear like in images, and this is characterized by a combination of ANSI CR and on/off CR. Knowing how dark in an absolute level a display can go doesn't characterize that in any way.
Reply
Reply
post #4 of 54
10/4/09 at 7:24pm
Thread Starter 
Thanks so far on the good answers..

I should explain...

I have possible access to a very high end DLP D-Cinema certified projector. It has a high lumen output which is not really adjustable without using ND filters. The lamp house is integrated and the output is 2 levels, high and higher

The screen is 2.35 and correctly small based on the viewing distance.

So, with a overly high light output designed for larger screens, black level will be important in scenes that are almost completely dark. Say scenes where nothing is over 20IRE. Then the black level will really stand out and be obvious.

I am fairly good with a high fL output for whites, within reason of course.

So not only do I want to do a reality check for the obvious, that the 100IRE output level is not going to cause sunburn, but I need to make sure of the black level, which in this case might be more of a issue then the 100IRE level.

I dont suppose anyone knows of any SMPTE standards for this for film for example ?
Reply
Reply
post #5 of 54
10/4/09 at 7:53pm
SMPTE standard for DCinema is IIRC 14 f-L

The DCinema 2K units typically output 20,000 lumens and do ~2,000:1 CR

14 f-l /2000 = 0.007 f-l on an a 50' wide screen
Reply
Reply
post #6 of 54
10/4/09 at 8:56pm
Thread Starter 
Yes, 14fL for open gate on 35mm, 30fL for 70mm.. But are they any standards for maximum black ? I dont think so. Maybe more of a print quality standard ?

This D-Cine was made for post house use, so its quoted 5000 Lumens at "High" and a quoted 3000:1, but I never trust CR numbers. Its brand new technology, I would rather not discuss make or model.
Reply
Reply
post #7 of 54
10/4/09 at 9:11pm
SMPTE 196M states 12 to 22 fL for cinemas with review rooms at 16 fL +- 2. The minimum CR is stated as 600:1 for review rooms.

16 fL / 600 = 0.027 fL
So 0.027 fL according to 196M-2003
Reply
Reply
post #8 of 54
10/4/09 at 9:21pm
Quote:
Originally Posted by HoustonHoyaFan View Post

SMPTE 196M states 12 to 22 fL for cinemas with review rooms at 16 fL +- 2. The minimum CR is stated as 600:1 for review rooms.

16 fL / 600 = 0.027 fL
So 0.027 fL according to 196M-2003

If spec is truly +/- 2, then minimum should be 0.03 fL.

My question is of what use is this beast if not taking advantage of it's large-screen filling abilities?
Reply
Reply
post #9 of 54
10/5/09 at 2:54am
Quote:
Originally Posted by LilGator View Post

My question is of what use is this beast if not taking advantage of it's large-screen filling abilities?

It would seem you assuming that the only advantage a DCI unit has, over the typical PJs we see represented in this particular section of AVS, is light output.

You would be very, very, wrong indeed.
Reply
Reply
post #10 of 54
10/5/09 at 2:59am
Thread Starter 
Wow Houston, thanks for a reference to the actual SMPTE standard, all these years as a SMPTE member I never actually looked it up !!

Besides reading the standard, doing a google on it brought up a number of really interesting other papers and articles !

Gotta love stuff like that... Good 1.5 hours of quality reading...

However...

What would be a excellent black level be for state of the art in digital cinema ?

pjpoes stated he was getting .002fL..

Does anyone have some good actual measurement data on black levels in a good setup ?
Reply
Reply
post #11 of 54
10/5/09 at 3:10am
Thread Starter 
"My question is of what use is this beast if not taking advantage of it's large-screen filling abilities?"

There is a long list of reasons using a DLP Cinema® certified projector is a good, but expensive, thing to do.

It has HD-SDI and does 23.98 as a primary function, right into the engine, not just some add on board. I am using a Teranex for upconversion of DVD's and having that input format is critical.

I am considering using a modded HD-SDI out BluRay and taking the 1080I59.94 and using the Teranex to do 3/2 into 1080P23.98 and delivering it directly to the projector.
Reply
Reply
post #12 of 54
10/5/09 at 4:29am
According to UltimateAV the black level of my RS2 was 0.0008fL. HomeTheater had it at 0.001fL, which I guess rounds up. Given the RS2 has the best blacks I've had, yet I can still do shadow puppets, I would class that as my ongoing minimum.
Reply
Reply
post #13 of 54
10/5/09 at 5:40am
Steve. For them to know it, they would need to measure for your specific sample of projector with your screen size and gain.
Reply
Reply
post #14 of 54
10/5/09 at 6:59am
Quote:
Originally Posted by mark haflich View Post

Steve. For them to know it, they would need to measure for your specific sample of projector with your screen size and gain.

Exactly. Steve, while you have a very nice room decor wise, (seen pics) there is no way you're getting even close to that black level in your room because of no light control and LED's through out (even with the FireHawk).
Reply
Reply
post #15 of 54
10/5/09 at 8:10am
Not only that, with the uniformity of those units, it really depends where on the screen you take your readings.
Reply
Reply
post #16 of 54
10/5/09 at 10:02am
Quote:
Originally Posted by coldmachine View Post

It would seem you assuming that the only advantage a DCI unit has, over the typical PJs we see represented in this particular section of AVS, is light output.

You would be very, very, wrong indeed.

I understand that- I was looking for a list of these advantages.

Say a 10-ft wide 2.35 screen, this DCI unit set up beside a Sim2 Lumis, Samsung SP-A900B, and Planar PD8150. Add appropriate ND filters or iris adjustments for all to yield 16fL.

Using Blu-ray content (delivered however preferred to each machine), how would this play out?

I'm genuinely curious as to the advantages (and disadvantages) there would be here.
Reply
Reply
post #17 of 54
10/5/09 at 10:23am
To have a meaningful comparison there is no point looking at some of those entry level units.

It would make more sense to look at a Lumis, HT5k, Titan Ref, Titan Lightning, PD units and machines of that ilk. Some of those will provide a superior overall performance to a DCI unit

I also think that 10ft may be rather small to fully appreciate the full capability of these machines.

This topic has been mentioned here before, but degenerates into the normal J6P CR fixation.
Reply
Reply
post #18 of 54
10/5/09 at 10:32am
Quote:
Originally Posted by coldmachine View Post

Its been mentioned here before, but degenerates into the normal J6P CR fixation.

OK... then I'll take a shot as "those from on high" can't seem to be bothered.

1. light output (but equalized in this test)
2. ANSI contrast
3. MTF (related to ANSI?)
4. Optics: less or no CA, sharpness, uniformity
5. color accuracy
6. Superior electronics/chip that reduce motion blur/3:2 judder
7. Uniformity

Just guessing here as even the comparison machines CM mentioned are several levels out of my league.
Reply
Reply
post #19 of 54
10/5/09 at 11:00am
Quote:
Originally Posted by xymox View Post

What would be a excellent black level be for state of the art in digital cinema ?

pjpoes stated he was getting .002fL..

Let's put it this way, a new JVR RS20 is capable of let's be conservative and say 30,000:1. If we assume it's set up for 16ftL (reference), that puts the black level down at 0.00053ftL. And some still aren't satisfied with it.

CRTs FPs were in the 100,000's to even around 1,000,000:1. Those are still the gold standard for black level, and that put's the black level at around 0.000016ftL.

Quote:


Does anyone have some good actual measurement data on black levels in a good setup ?

Not really, because it's very hard to find meters that can accurately read down to even 0.0005ftL. The Konica Minolta LS-100 supposedly goes down to 0.0003 ftL (0.001 cd/m2 ) but IIRC it's accuracy gets questionable down there.
Reply
Reply
post #20 of 54
10/5/09 at 11:26am
Quote:
Originally Posted by coldmachine View Post

I also think that 10ft may be rather small to fully appreciate the full capability of these machines.

That was the point of my question. At a relatively small screen size, what are the "fully appreciated" advantages over even entry level DLPs?
Reply
Reply
post #21 of 54
10/5/09 at 11:37am
Quote:
Originally Posted by stanger89 View Post

...CRTs FPs were in the 100,000's to even around 1,000,000:1...

That is an Urban Legend. At the height of their popularity the CRT FP with the highest on/off CR specification was the Sony G90 at 40,000:1, the other 9" models were specced at 30,000:1. 8" and smaller CRTs was specced at 10,000:1 to 30,000:1

Properly setup and d65 calibrated for grayscale, color, and broadcast monitor shadow detail most CRT FP measured ~10,000:1

The recent advent of external gamma correction devices has apparently enabled very high CRT on/off CR. IIRC darinP estimated a gamma modified G70 at 700,000:1. My G70 (non modified) setup by the Chief Technician at a post prod company measured ~9,000:1 and 17,000:1 with significant black crush.
Reply
Reply
post #22 of 54
10/5/09 at 1:09pm
Quote:
Originally Posted by HoustonHoyaFan View Post

The recent advent of external gamma correction devices has apparently enabled very high CRT on/off CR. IIRC darinP estimated a gamma modified G70 at 700,000:1.

There's at least one member here who's posted their gamma corrected CRT measured over 700,000:1 with a "bad" blue tube, ie one that was "glowing" when it shouldn't have been.
Reply
Reply
post #23 of 54
10/5/09 at 1:32pm
Quote:
Originally Posted by stanger89 View Post

There's at least one member here who's posted their gamma corrected CRT measured over 700,000:1 with a "bad" blue tube, ie one that was "glowing" when it shouldn't have been.

The 700,000:1 sounds like darinP's work. IIRC it was not a direct measurement but a comparative estimate based on adding ND filters to a RS2 until it displayed a similar BL to the G70 but I am fuzzy. Hopefully darinP can chime in on his measurement techniques.

If someone else "measured" a CRT with that kind of CR I would be curious how they did it.
Reply
Reply
post #24 of 54
10/5/09 at 1:53pm
Ah, I found it, it was by overclkr in the Contrast measurements thread:
http://www.avsforum.com/avs-vb/showt...3#post14656183

CR was measured by a Minolta directly into the lens. The green tube was around 3.5 million:1
Reply
Reply
post #25 of 54
10/5/09 at 8:50pm
Thread Starter 
Any CR numbers as high as you guys are discussing are insanely hard to measure and almost completely unbelievable. Photo Research has a nice instrument which I have used that could do it. The PR-810L and can do 0.000001 to 518,400 fL and 512,000,000,000:1 contrast ratio. Its also handy cuz its handheld and portable. http://www.photoresearch.com/current/pr810L.asp But you need so many other things to make this measurement. God,, if a LED inside the unit someplace was glowing, its light might escape out of the case and pollute the measurement !.. Measuring really low fL levels with the right gear is insane, you need a special light tight room, you need to wear a black space suit kinda outfit. Even really weird things like body heat ( IR ) and IR from the device under test can pollute the measurements unless filtered out. In Plasma devices the UV needs to be filtered out.

For someone to have measured hyper high CR outside of laboratory conditions with a max output from a CRT makes me dubious about the results.

That said.. I would know about CRT black levels. I did make one of the best CRT FP's And when a CRT tube is off, 0 IRE, its not completely "OFF" as you approach G2 cutoff its not a sharp edge. But yea, mostly its OFF.. Some stray electrons do illuminate the face of the tube just because of the 2nd anode being 30Kv, but thats about it. Well ok, the tube would act like a cosmic ray detector and a few photons would be produced by a stay particle from space heheheheh... But these full of measurments are not a real CR !,, Thats full off. Once a tube is in use, its a very analog thing. The phosphor heats up and glows even after the white goes away. So quickly switching between full white and black is a whole different CR then slowly switching back and forth. Tubes are very non-linear and have temporal changes that need to be taken into account when doing measurements. A CRT is a very difficult moving target for measurements. Did you know that a CRT xy color point moves ever so slightly when its phosphor is hot then when its cold ? This changes in 100ms to seconds. Its also specific to the spot on the face of the CRT that is heated ( illuminated ).

Digital devices are much more digital Not that they are better. Our visual system is very analog and nothing could be more foreign then a PWM light source from a DLP mirror.

But lets stay on topic.

We have a measured fL of 0.0008fL and HomeTheater had it at 0.001fL. These sound like the bottom of the meters ability and both these mags I dont think have a PR-810L. This does however give me a good idea of a reasonable expectation of what black should be.

Anyone else happen to have any real measurements of a exceptional system ?
Reply
Reply
post #26 of 54
10/6/09 at 9:12am
Quote:
Originally Posted by xymox View Post

Any CR numbers as high as you guys are discussing are insanely hard to measure and almost completely unbelievable. Photo Research has a nice instrument which I have used that could do it. The PR-810L and can do 0.000001 to 518,400 fL and 512,000,000,000:1 contrast ratio. Its also handy cuz its handheld and portable. http://www.photoresearch.com/current/pr810L.asp But you need so many other things to make this measurement. God,, if a LED inside the unit someplace was glowing, its light might escape out of the case and pollute the measurement !.. Measuring really low fL levels with the right gear is insane, you need a special light tight room, you need to wear a black space suit kinda outfit. Even really weird things like body heat ( IR ) and IR from the device under test can pollute the measurements unless filtered out. In Plasma devices the UV needs to be filtered out.

That was essentially the point I was trying to make.

Quote:


For someone to have measured hyper high CR outside of laboratory conditions with a max output from a CRT makes me dubious about the results.

Measuring CR can be very different than measuring absolute black level. The referenced measurement was done by measuring directly out of the tube, not off the screen. Thus the "black" measurment was dramatically higher. It's much easier to both find sensors/meters, and to perform the measurement with the higher light levels from measuring projector output, instead of screen illuminance.
Reply
Reply
post #27 of 54
10/6/09 at 10:15am
Thread Starter 
Yeap.... measuring low light levels for doing CR is a tricky business. Not to mention the zillions of ways to cheat with the numbers and also the different standards...

Well..... My thread here has been made kinda moot... I have confirmation that I will not be using the projector I thought. There is a better way to go with a option for far less light output. Smaller light source..

Soooooo..... now I am not concerned about my absolute black level cuz I know it will be very very low. Im still gonna end up rather high in fL on a 108" 1.0 gain Screen Research diag 2.35 with about 50fL but thats ok for me. I actually like a slightly hot picture as long as the blacks are under control.

I am getting the manufacturer, who needs to remain anonymous, to do real measurements of the projectors black level lumen output using a low setting for lamp power. I will post it here when I get it. They have access to real measuring instruments so it will be accurate.

This thread starting me thinking that the black level is a really critical thing and with the right equipment is easy to measure. This should be included on all specs.... Yea right,,, like thats ever gonna happen !!!!!!!!

So for me,,, I think im done with my original question... Thanks for the answers.. I will come back to this thread and post what they give me for black level output and what lumen level for white.. But unfortunately I cannot mention the projector

Thanks !
Reply
Reply
post #28 of 54
10/6/09 at 10:36am
Quote:
Originally Posted by xymox View Post

This thread starting me thinking that the black level is a really critical thing and with the right equipment is easy to measure. This should be included on all specs.... Yea right,,, like thats ever gonna happen !!!!!!!!

That's not gonna happen because it's impossible. There are too many variables in the pj/screen/room installation.
Reply
Reply
post #29 of 54
10/6/09 at 11:29am
Quote:
Originally Posted by stanger89 View Post

Ah, I found it, it was by overclkr in the Contrast measurements thread:
http://www.avsforum.com/avs-vb/showt...3#post14656183

CR was measured by a Minolta directly into the lens. The green tube was around 3.5 million:1

I remember that thread now. I agree with odyssey's comments.

Here is a link to spec table for Sony CRT FPs
http://www.curtpalme.com/PJSpecs_Sony.shtm
Reply
Reply
post #30 of 54
10/6/09 at 11:33am
Quote:
Originally Posted by xymox View Post

...This thread starting me thinking that the black level is a really critical thing and with the right equipment is easy to measure. This should be included on all specs.... Yea right,,, like thats ever gonna happen !!!!!!!!

Black level is already included in the spec for every projector. Its called CR.

Black Level = White Level / CR.

Any black level spec with out the corresponding white level would be useless
Reply
Reply
New Posts  All Forums:Forum Nav:
  Return Home

AVS Top Picks

AVS › AVS Forum › Display Devices › Digital Hi-End Projectors - $3,000+ USD MSRP › Max acceptable fL for black ?