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Official JVC X30 / RS45 owner's thread! - Page 142

post #4231 of 4435
Mike,

Watching Baraka, I actually had to tune down my Darbee from 60 to 45% to minimize noise/artifacts. Now the picture is less "digital".
post #4232 of 4435
Quote:
Originally Posted by JonStatt View Post


Jason, do I need sunglasses when I pop over to yours for a viewing? smile.gif

some are going to think it's too bright. cool.gif The irony is, I have very good night vision. Since I blacked out my ceiling (HP screen is just inches from the ceiling) i'm finding I can crank the iris further down or in the case of the Sharp 30K (950 D65 lumens) run the iris on high contrast to cut down some of the light or run it in low lamp.

also, I have the RS55 in a location where it's not optimal for max gain, that spot gets reserved for the 3D projector, so there is definite drop off as well.
post #4233 of 4435
Quote:
Originally Posted by JonStatt View Post

Hmmm...for some TVs your comparison is right. Not quite all TVs though because some have auto-dimming backlights. So it depends on the TV. If your TV does change the backlight on its own depending on the scene, and you force the backlight up with the adjustment to get more brightness, you restrict the contrast. This latter scenario is more akin to the auto-iris of Sony projectors. JVC always proudly announces its contrast is achieved natively without the need for varying backlights or apertures dynamically etc.

Fundamentally the bulb has two wattages it runs at. Consider that everything else in the projector remains the same, you are just changing the wattage of the bulb. However, in Jason's scenario, he can only clamp the iris down when his bulb is on high. This is because he likes a brighter image. For him the only way to get both a bright and contrasty image together is to have high bulb with closed aperture.

If you are not a brightness freak, or have a smaller screen, you can get the aperture closed down on low bulb. One scenario you do NOT want is low bulb and a wide open aperture. Then you are throwing away a significant amount of contrast. To avoid this scenario either you run at high bulb mode and/or use a higher gain screen material. I am somewhat stunned that Jason still needs high bulb to get enough brightness with the aperture closed on a 2.8 gain screen!

Jason, do I need sunglasses when I pop over to yours for a viewing? smile.gif

so, trying not to turn this into a complicated mess(too late), are you saying closing the iris adds to the contrast, regardless of how much light the bulb is outputting? I thought the improved contrast was due to less light being emitted, therefore less reflected/scattered light hitting the screen where it shouldn't.

to be perfectly honest, I started with low bulb(high is not an option for me, way too noisy) with the aperture wide open. I only closed it down to -12 after reading about 'improved contrast'. I settled on -12 because with a solid black screen, that seemed to be the point where going darker didn't make black any blacker. but I never would have done this if not for reading on here. I still think the image looks better with the aperture fully open.

i'm just really confused by this whole thing. I thought the aperture was just a fine adjustment for how bright the bulb is. high/low is a gross adjustment for the same thing. let's say for comparison, low bulb, full aperture puts out 800lumens. and high bulb -15 aperture also puts out 800lumens. assuming this was possible/true, why wouldn't I see an identical image on my screen. they both have the same light output, and nothing else would change.

still not sure 'significant' is the right term to describe the change in contrast with the iris open/closed. on my set up discs the contrast seemed exactly the same. the whole image was just uniformly dimmed, exactly like reducing the backlight/cell light on a flat screen. except that there's is a much narrower range on the projector, so it still looks good even on the lowest setting.

I know i'm a difficult student, but I care infinitely more about the why than the what. and I still don't understand why reducing light with the iris is different than reducing light with the bulb
post #4234 of 4435
Quote:
Originally Posted by fierce_gt View Post

so, trying not to turn this into a complicated mess(too late), are you saying closing the iris adds to the contrast, regardless of how much light the bulb is outputting?

I'm not JonStatt, but 'yes'.
Quote:
Originally Posted by fierce_gt View Post

I thought the improved contrast was due to less light being emitted, therefore less reflected/scattered light hitting the screen where it shouldn't.

Less 'Scattered' light emitted, not just 'less light' emitted. If the amount of internal scattered light that escapes onto the screen image was unaffected by the iris position, then there would be no contrast change.
Quote:
Originally Posted by fierce_gt View Post

i'm just really confused by this whole thing. I thought the aperture was just a fine adjustment for how bright the bulb is.

It is that also.
Quote:
Originally Posted by fierce_gt View Post

high/low is a gross adjustment for the same thing. let's say for comparison, low bulb, full aperture puts out 800lumens. and high bulb -15 aperture also puts out 800lumens. assuming this was possible/true, why wouldn't I see an identical image on my screen. they both have the same light output, and nothing else would change.

Probably due to your room (set up and reflections) and your subjective perceptions.
Also, where you mounted your PJ also can have an effect on contrast (and brightness/blacks) depending on if you mount it at the long or short throw range of the zoom....and depending on that, the Iris may have a lesser or greater affect on contrast improvements.
Law of diminishing returns if you will.
Quote:
Originally Posted by fierce_gt View Post

I know i'm a difficult student, but I care infinitely more about the why than the what. and I still don't understand why reducing light with the iris is different than reducing light with the bulb

Again, reducing the light with the bulb doesn't affect the light scatter inefficiencies built into the optical path, but closing down the Iris in said optical path does have an effect on how much light scatter escapes onto the screen image, no matter what HI/LOW lamp you are using.

In a perfect world PJ's would have no light scatter escaping, though they would need to build a mini black hole into the optical path to do that. Until then, Irises can help.
post #4235 of 4435
Also, on most PJ's with manual irises, it's better to have more lumens to spare and clamp down on them with a manual iris, as you can gain a contrast improvement advantage.
As the lamps dim and you slowly open up the iris to maintain your starting lumen level (brightness on bright scenes), you will lose some contrast performance. Whether it is noticed by you or others is another matter.

As to the reason why zombie runs his PJ at high lamp and clamps down the iris from there? Well, I would assume that with more lumens to spare (high lamp) he would have to close down the iris even further (than low lamp) than what he would at the low lamp setting. With a iris closed down even further, he should be seeing (or measuring) a contrast improvement vs low lamp with the iris a few clicks more open.
post #4236 of 4435
Quote:
Originally Posted by fleaman View Post

I'm not JonStatt, but 'yes'.
Less 'Scattered' light emitted, not just 'less light' emitted. If the amount of internal scattered light that escapes onto the screen image was unaffected by the iris position, then there would be no contrast change.
It is that also.
Probably due to your room (set up and reflections) and your subjective perceptions.
Also, where you mounted your PJ also can have an effect on contrast (and brightness/blacks) depending on if you mount it at the long or short throw range of the zoom....and depending on that, the Iris may have a lesser or greater affect on contrast improvements.
Law of diminishing returns if you will.
Again, reducing the light with the bulb doesn't affect the light scatter inefficiencies built into the optical path, but closing down the Iris in said optical path does have an effect on how much light scatter escapes onto the screen image, no matter what HI/LOW lamp you are using.

In a perfect world PJ's would have no light scatter escaping, though they would need to build a mini black hole into the optical path to do that. Until then, Irises can help.

First off, I really appreciate the reply and the effort put into it. thank you.

now a couple follow up questions/comments.
-I have not actually experimented with low bulb/full aperture vs high bulb/closed aperture and have no idea at what point they would have the same lumen output, those comments were for demonstrative purposes only. I have not 'observed' that the image looks the same. I just couldn't understand why it wouldn't.
for what it's worth, I have my projector mounted at about 18feet from my 100" screen, so about 2feet less than max throw. I learned maybe a week before I received the projector that contrast improved at the max throw, had never heard of it before, so I did try to stay close to max while still giving myself a bit of a cushion to adjust.

-ok, so seems like this all boils down to this scattered light thing. I thought scattered light meant the light that bounced around your room and ended up on screen. I mean I still have a white ceiling, and turning the projector on makes my ceiling bright. there's even some light that will hit the ceiling when there is no screen, so I assumed that was the light scatter. some of the light from the projector is actually going directly to the ceiling, as well as some of the light reflecting off the screen going onto the ceiling. and then that light reflects back onto the screen. now for that kind of light, any reduction would lower my black levels, and increase contrast. But it sounds like light scatter with regards to the iris is different than this. like if I had a screen floating in the middle of a huge black space, where there essentially wasn't any walls or any other surfaces for light to bounce off of other than the screen, there would still be a reduction in black levels and an increase in contrast with the iris closed? is this due to a more focused beam of light? or light travelling through just the middle of the lens? or what? still really lost how blocking light is better than dimming light.

-last question. so, I've basically dimmed my image using the iris because of my room reflections. namely the white ceiling. I will be painting my ceiling dark in a couple weeks. my iris is set to -12, and i'm 'living with' the dimmer image because a brighter image causes too much light to be reflected around my room and raising the black level on my screen. after painting, i'm going to experiment again with a more open iris. my question is what's the best way to determine the 'right' setting? if I can't see an improvement in blacks, should I stop there? or is there technically always better contrast at the most closed setting. i'm certain the image will be bright enough at any setting but it certainly 'pops' with the open aperture. I know at the end of the day it's really my preference, but there's been plenty of other examples of things that once I learned the 'right way' to set them, I could never go back. sharpness for one comes to mind. so I at least want to try it and see if I get used to it before I just go back to a more dynamic looking open iris.

once again, thank you so much for all the time and effort. I really hope i'm not coming across as argumentative or doubtful. i'm just the kind of person that likes to understand the whole thing, the more technical the better.
Edited by fierce_gt - 6/28/13 at 11:34pm
post #4237 of 4435
Room reflections is not what we would call light scatter within the optics. That's why I was always mentioning light scatter along with the 'within the optic path', or within 'the screen image' (not from the room), etc.

While room reflections are technically a form of light scatter, we really tend to call 'em ambient light, reflections, room reflections, etc. I've never really seen anyone call 'em 'light scatter', even though they technically wouldn't be wrong in doing so.

Even with room reflections, changing from LOW to HI lamp (and not changing anything else) shouldn't really affect your on/off contrast.

Back to light scatter with optics> I'm not really sure how to explain it more eloquently as I'm not really an expert on it. But think of it this way: You have lamp that's outputting unfocused light, it is sent through and optical engine or assembly via lenses and mirrors to focus and channel that light to the imaging chips (DLP, LCD, LCOS, etc.), which is then hopefully sent out the lens in a focused and clean way. In regards to contrast you have to look at how 'black' or the absence of light is produced. With DLP the chip (DLP) is literally a million+ tiny mirrors that mechanically turn on/off by angling the light reflected to it around 12* (degrees) or so. When 'on' the mirror (each mirror is 1 pixel on a DLP chip) is either at 0* or 12* (I can't remember which is which). When in the 'off' position the mirror points the light to a blackened part of the optic assy and in a perfect world the unwanted light would disappear in that black part of the optic engine and zero light would reflect out of the 1 pixel spot that the 'off' mirror is at, and pure black would exit the lens and produce pure black at the screen (assuming it is also floating in a black hole!).

Of course this doesn't happen, not even close. At the 'off' pixel some light is still being reflected, and the black area of the optic assy that the 'off' pixel shining light into is also reflecting some light back (if you don't believe me, turn all the lights off in a darkroom, and shine a flashlight on black velvet, you'll still be able to see it), so that unwanted light is like the ambient light in your living room. Even a total black living room will still light up---if you shine flashlight at the wall, you'll still see the wall.
What's worse is that for obvious reasons, you can't make a totally black optical assy. For one, you can't make the lenses black! Even the lenses reflect light in unwanted directions, producing light scatter.

So the easiest way to think of light scatter in optics is like the ambient reflective light bouncing around in your HT room, then onto your screen, decreasing your contrast performance. In the same way, light scatter within the optical assy of a projector is also unwanted light bouncing around, but in this case it is within the image being projected out of the lens. The ambient light reflections of your HT room only make it worse!

Also, as with room reflections, changing your lamp between HI/LOW isn't gonna effect light scatter within the optic assy either.
post #4238 of 4435
Quote:
Originally Posted by fleaman View Post


Again, reducing the light with the bulb doesn't affect the light scatter inefficiencies built into the optical path, but closing down the Iris in said optical path does have an effect on how much light scatter escapes onto the screen image, no matter what HI/LOW lamp you are using.

In a perfect world PJ's would have no light scatter escaping, though they would need to build a mini black hole into the optical path to do that. Until then, Irises can help.

good point, this is why JVC put in the 2nd lamp iris in the mid-range models. It helps reduce light scatter before it enters the optical path.

These photos are from Cine4home's tear down of the RS55/X70. # 2 is the 'lamp iris' and #1is the regular iris found in base models. (RS55/RS56 have both)

Vergleichsspecial_clip_image040.jpg

Lamp iris

Vergleichsspecial_clip_image042.jpg


In regard to perceived contrast, the white ceiling is un-doing all the good stuff the JVC is capable of. I recently blacked out my ceiling and floor, it makes a substantial difference comparing before/after.
post #4239 of 4435
I'm gonna quote myself here>
Quote:
Originally Posted by fleaman View Post

So the easiest way to think of light scatter in optics is like the ambient reflective light bouncing around in your HT room, then onto your screen, decreasing your contrast performance. In the same way, light scatter within the optical assy of a projector is also unwanted light bouncing around, but in this case it is within the image being projected out of the lens. The ambient light reflections of your HT room only make it worse!

And as for the reason a Iris reduces light scatter? Well, lets take ambient light reflections in your room as an example. Imagine your whole room is the optical assy/engine of a large projector....your PJ is the lamp/light source and your screen is the lens, but in this case lets say your screen is clear glass (like the outside lens on your PJ) and is about the same size as your lens (couple inches in dia).

So, obviously some light is reflecting around your room and decreasing your contrast onto your glass screen. Lets say there's 6ft between your PJ and the 2" glass screen. Now, I hang a black velvet sheet say 1ft from the 2" glass screen (so, 5ft from the PJ) and cut a 2" hole in that black velvet so that only the PJ image goes through that hole, while much (but not all) of the room reflected light is blocked by that black velvet curtain. Even though there will still be room reflections getting into that hole, it will be a LOT less than if that black velvet sheet wasn't there.
post #4240 of 4435
Quote:
Originally Posted by fleaman View Post

Room reflections is not what we would call light scatter within the optics. That's why I was always mentioning light scatter along with the 'within the optic path', or within 'the screen image' (not from the room), etc.

While room reflections are technically a form of light scatter, we really tend to call 'em ambient light, reflections, room reflections, etc. I've never really seen anyone call 'em 'light scatter', even though they technically wouldn't be wrong in doing so.

Even with room reflections, changing from LOW to HI lamp (and not changing anything else) shouldn't really affect your on/off contrast.

Back to light scatter with optics> I'm not really sure how to explain it more eloquently as I'm not really an expert on it. But think of it this way: You have lamp that's outputting unfocused light, it is sent through and optical engine or assembly via lenses and mirrors to focus and channel that light to the imaging chips (DLP, LCD, LCOS, etc.), which is then hopefully sent out the lens in a focused and clean way. In regards to contrast you have to look at how 'black' or the absence of light is produced. With DLP the chip (DLP) is literally a million+ tiny mirrors that mechanically turn on/off by angling the light reflected to it around 12* (degrees) or so. When 'on' the mirror (each mirror is 1 pixel on a DLP chip) is either at 0* or 12* (I can't remember which is which). When in the 'off' position the mirror points the light to a blackened part of the optic assy and in a perfect world the unwanted light would disappear in that black part of the optic engine and zero light would reflect out of the 1 pixel spot that the 'off' mirror is at, and pure black would exit the lens and produce pure black at the screen (assuming it is also floating in a black hole!).

Of course this doesn't happen, not even close. At the 'off' pixel some light is still being reflected, and the black area of the optic assy that the 'off' pixel shining light into is also reflecting some light back (if you don't believe me, turn all the lights off in a darkroom, and shine a flashlight on black velvet, you'll still be able to see it), so that unwanted light is like the ambient light in your living room. Even a total black living room will still light up---if you shine flashlight at the wall, you'll still see the wall.
What's worse is that for obvious reasons, you can't make a totally black optical assy. For one, you can't make the lenses black! Even the lenses reflect light in unwanted directions, producing light scatter.

So the easiest way to think of light scatter in optics is like the ambient reflective light bouncing around in your HT room, then onto your screen, decreasing your contrast performance. In the same way, light scatter within the optical assy of a projector is also unwanted light bouncing around, but in this case it is within the image being projected out of the lens. The ambient light reflections of your HT room only make it worse!

Also, as with room reflections, changing your lamp between HI/LOW isn't gonna effect light scatter within the optic assy either.

just when I think i'm about to understand, you start talking about room reflections again, haha.

so, we're using the DLP, but I guess all digital projectors are using a similar reflected image so it works the same way through the optics right? if it were possible to angle more than 12*, that would help make black blacker? since the iris reduces the angle between the chip and the opening, it makes this 12* shift more effective.

i'm still unclear what i'm supposed to do with this information. close my iris down all the way? or how do I decide/determine the point it no longer helps? is there any situation where a more open iris would be good? <-- specifically i'm wondering if my room reflections raise the black level, and i'm never going to get better contrast reducing the iris because of that, so would a more open iris, and brighter whites help?

if this is really about the 12* angle being larger relative to the angle from chip to aperture, then I would be less(?) likely to notice an improvement at max throw, since I've already reduced the angle by zooming out?
post #4241 of 4435
Quote:
Originally Posted by zombie10k View Post

In regard to perceived contrast, the white ceiling is un-doing all the good stuff the JVC is capable of. I recently blacked out my ceiling and floor, it makes a substantial difference comparing before/after.

But in theory it wouldn't matter for on/off contrast to an all black image. Like if you turned off the PJ in a white room that was 100% light controlled (no ambient light). This is how on/off is measured of course.

I know you know this, just mentioning it for others smile.gif

Though in the real world we don't watch all white and then all black images, so of course in mixed content images, fixing room reflections makes a HUGE difference.
post #4242 of 4435
Quote:
Originally Posted by fierce_gt View Post

so, we're using the DLP, but I guess all digital projectors are using a similar reflected image so it works the same way through the optics right? if it were possible to angle more than 12*, that would help make black blacker? since the iris reduces the angle between the chip and the opening, it makes this 12* shift more effective.

No, the 12* is just enough for a DLP chip to angle it away from the PJ path into a dedicated 'black' non-reflective area, but again, there's no true black holes in life, so unwanted reflections due to the less than perfect black 'dead' areas of a DLP optic engine still get scattered about.

DLP is a reflective chip, hence the mirrors pivot on/off to turn the pixels on/off. DLP turns the pixel 'off' by angling the light to a black box area of the optic assy. With LCOS or LCD, it's a translucent image chip (not sure if that's the proper term?). So the light patch goes THROUGH the chip and the LCD crystals turn on/off. When 'off' in theory the LCOS pixel goes 'black' and no light passes. But some does, and also there is light scatter after it passes through the LCD/LCOS chip on it's way out of the optic engine.
post #4243 of 4435
Quote:
Originally Posted by zombie10k View Post

good point, this is why JVC put in the 2nd lamp iris in the mid-range models. It helps reduce light scatter before it enters the optical path.

These photos are from Cine4home's tear down of the RS55/X70. # 2 is the 'lamp iris' and #1is the regular iris found in base models. (RS55/RS56 have both)

In regard to perceived contrast, the white ceiling is un-doing all the good stuff the JVC is capable of. I recently blacked out my ceiling and floor, it makes a substantial difference comparing before/after.

thanks for the visuals. i'm wondering if the lamp iris is more effective than the lens iris, or is it just taking it to the next step? I mean, if you had your choice of only one, would you take lens or lamp? obviously both is better.

as for the ceiling, I've done the the first 4feet and it definitely made a large difference. i'm not expecting as much improvement when I do the rest, but getting the jvc has definitely inspired me to try. with my old Epson it was the brightest source of light still. with the jvc i'm not so sure. I can still see shadows cast on an all black screen, but I feel the darker ceiling would still help me focus on the screen more. either way, it's on my do-to list, and well, today was the last day of school, so, i'm off until sept. perks of being a teacher
Quote:
Originally Posted by fleaman View Post


So, obviously some light is reflecting around your room and decreasing your contrast onto your glass screen. Lets say there's 6ft between your PJ and the 2" glass screen. Now, I hang a black velvet sheet say 1ft from the 2" glass screen (so, 5ft from the PJ) and cut a 2" hole in that black velvet so that only the PJ image goes through that hole, while much (but not all) of the room reflected light is blocked by that black velvet curtain. Even though there will still be room reflections getting into that hole, it will be a LOT less than if that black velvet sheet wasn't there.

this kind of makes me think the lens iris IS more effective, since it's further away from the source and closer to the screen, albeit by mere cm's. I do say this makes me wonder about the 'ultimate' install. if there would be benefit to having the projector installed in the adjacent room, shining through a small rectangle in line with my screen. probably way beyond what's needed, but makes me think if nothing else.
post #4244 of 4435
Quote:
Originally Posted by fierce_gt View Post

i'm still unclear what i'm supposed to do with this information. close my iris down all the way? or how do I decide/determine the point it no longer helps? is there any situation where a more open iris would be good? <-- specifically i'm wondering if my room reflections raise the black level, and i'm never going to get better contrast reducing the iris because of that, so would a more open iris, and brighter whites help?

Well, for one you mentioned you're close to the max throw range of your PJ. This already gives you increased contrast performance, though a lower lumen performance.

A more open iris would usually be better on bright content, like sports, bright animation, etc. You're not gonna notice the decreased black performance/contrast as much (if at all), and it's usually preferable to what sports as a bright image, not a dim image.

A more closed iris would usually be better for dark content, sci fi, etc. It is here that not only will you notice decreased contrast performance of an open iris, but also the higher black level.
Quote:
Originally Posted by fierce_gt View Post

if this is really about the 12* angle being larger relative to the angle from chip to aperture, then I would be less(?) likely to notice an improvement at max throw, since I've already reduced the angle by zooming out?

Ignore the 12* info. That only pertains to the internal workings of a DLP chip, it has no correlation to anything regarding PJ set ups.
post #4245 of 4435
Quote:
Originally Posted by fleaman View Post

But in theory it wouldn't matter for on/off contrast to an all black image. Like if you turned off the PJ in a white room that was 100% light controlled (no ambient light). This is how on/off is measured of course.

I know you know this, just mentioning it for others smile.gif

Though in the real world we don't watch all white and then all black images, so of course in mixed content images, fixing room reflections makes a HUGE difference.

My screen is very close to my ceiling, so any bit of light on the screen was hitting the ceiling and reflecting back onto the screen. This was most evident with scope content on my 16:9 screen, the black bars were lighting up more than I would have liked to see. Now with the reflection control, they remain nice and dark even with bright scenes.

The JVC definitely does it's best impression with a black pit. cool.gif
post #4246 of 4435
Quote:
Originally Posted by fleaman View Post

No, the 12* is just enough for a DLP chip to angle it away from the PJ path into a dedicated 'black' non-reflective area, but again, there's no true black holes in life, so unwanted reflections due to the less than perfect black 'dead' areas of a DLP optic engine still get scattered about.

DLP is a reflective chip, hence the mirrors pivot on/off to turn the pixels on/off. DLP turns the pixel 'off' by angling the light to a black box area of the optic assy. With LCOS or LCD, it's a translucent image chip (not sure if that's the proper term?). So the light patch goes THROUGH the chip and the LCD crystals turn on/off. When 'off' in theory the LCOS pixel goes 'black' and no light passes. But some does, and also there is light scatter after it passes through the LCD/LCOS chip on it's way out of the optic engine.

so being that the jvc is lcos, does that make it less/more/as likely to benefit from closing the iris? are we talking about diffraction around the pixels in the lcd/lcos panels too?

i'm lost again as to why this helps if it's not about the angles. so you've got this mini black hole 12* to the side of the lens in the DLP. except it's not a black hole, and some light will reflect back and bounce out eventually. that explains why it's near impossible to make 'black' on screen. but i'm not seeing the connection between that and the iris, unless it's the relative angles. if the black hole was 24* away, wouldn't that mean less light would make it out since it's farther from the aperture?
post #4247 of 4435
Quote:
Originally Posted by zombie10k View Post

My screen is very close to my ceiling, so any bit of light on the screen was hitting the ceiling and reflecting back onto the screen. This was most evident with scope content on my 16:9 screen, the black bars were lighting up more than I would have liked to see. Now with the reflection control, they remain nice and dark even with bright scenes.

The JVC definitely does it's best impression with a black pit. cool.gif

I have a overhang. the screen is is only about 4inches away from the ceiling, but after about 4ft the ceiling becomes 2.5ft higher. I've left the higher point white, I know it's not affecting the screen as much, but it does light up the back of the room. that light will eventually make it's way back to the screen i'm sure, but I think it's probably unnecessary for me right now. I don't notice the black bars at all. in fact with the lens memory I've got the picture shifted up so much that the black bars are actually shining on the overhang in my ceiling(painted med dark brown) and it doesn't show up at all fortunately.
post #4248 of 4435
So just to summarise for clarity

Room reflections will affect the intrascene contrast. Nothing you change on the projector including the aperture will affect the amount this happens. It is proportional to the light output from the projector.

The aperture adjustment and where you set it, has nothing to do with the type of room you are using the projector in. Whether you have a blacked out room, or a white walled room, the aperture adjustment will always affect on/off contrast for the better as you close it down. The scattering referred to is entirely within the optical engine of the projector.

High and low bulb has no effect on contrast. But if the goal is to close the aperture as much as possible, you may only be able to get a bright enough image in high bulb.

If the aperture is closed too far such that light output is too low, the image will look faded and lacking dynamics even though the contrast is actually at its highest. This is because you need a minimum level of peak white "for your eyes" to be satisfied that the image is bright enough.

To set the aperture, start with the aperture fully closed, and display a scene with a good mix of light and dark. Increase the aperture until the image is considered bright enough for your tastes. Stop there. That's the best match of brightness and contrast.

By the very fact that the X45/55 achieve 50k:1 with the aperture fully closed, and the X75 achieves 90k:1 (less than double improvement despite being natively better wide open), you can infer that although the dual aperture benefits noticeably but the more effective aperture is the front lens one! I believe an X45 measures about 28K:1 wide open and 50K:1 fully closed at longest throw. This shows you how much the aperture helps on an LCoS projector
post #4249 of 4435
Quote:
Originally Posted by JonStatt View Post

So just to summarise for clarity
I've added comments for discussion
Quote:
Room reflections will affect the intrascene contrast. Nothing you change on the projector including the aperture will affect the amount this happens. It is proportional to the light output from the projector.
but if my contrast sucks because I have too much reflected light, wouldn't reducing the light by EITHER dimming the bulb(low mode) or closing the iris help?
Quote:
The aperture adjustment and where you set it, has nothing to do with the type of room you are using the projector in. Whether you have a blacked out room, or a white walled room, the aperture adjustment will always affect on/off contrast for the better as you close it down. The scattering referred to is entirely within the optical engine of the projector.
unless you have so much ambient light that the lowered black level is unnoticed... like shining a flashlight on the screen, or only raises the black level, thus reducing contrast. but that's not affecting whether or not it improves contrast, that's affecting whether or not you can SEE that improvement.
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High and low bulb has no effect on contrast. But if the goal is to close the aperture as much as possible, you may only be able to get a bright enough image in high bulb.
as long as room reflections aren't an issue. otherwise high bulb = brighter image = more light reflected back on screen = worse contrast

Quote:
If the aperture is closed too far such that light output is too low, the image will look faded and lacking dynamics even though the contrast is actually at its highest. This is because you need a minimum level of peak white "for your eyes" to be satisfied that the image is bright enough.
is it ever possible for this to not actually be the best contrast? is there a point where closing down the iris simply doesn't make blacks any blacker anymore? and if the picture is bright enough at this point, should this be where you stop?
Quote:
To set the aperture, start with the aperture fully closed, and display a scene with a good mix of light and dark. Increase the aperture until the image is considered bright enough for your tastes. Stop there. That's the best match of brightness and contrast.
what if the lowest setting is 'bright enough' but I don't notice any change in black from -15 to -12?
Quote:
By the very fact that the X45/55 achieve 50k:1 with the aperture fully closed, and the X75 achieves 90k:1 (less than double improvement despite being natively better wide open), you can infer that although the dual aperture benefits noticeably but the more effective aperture is the front lens one! I believe an X45 measures about 28K:1 wide open and 50K:1 fully closed at longest throw. This shows you how much the aperture helps on an LCoS projector
at least on paper... tongue.gif
post #4250 of 4435
Quote:
Originally Posted by fierce_gt View Post

I've added comments for discussion

but if my contrast sucks because I have too much reflected light, wouldn't reducing the light by EITHER dimming the bulb(low mode) or closing the iris help?

It is proportional. If you have double the light output, you will have doubled the reflections. It won't affect the on/off contrast as all you have done is lift black and white proportionally.
Quote:
unless you have so much ambient light that the lowered black level is unnoticed... like shining a flashlight on the screen, or only raises the black level, thus reducing contrast. but that's not affecting whether or not it improves contrast, that's affecting whether or not you can SEE that improvement.

Well shining a flashlight raises the white level too as the amount of light you see from seated actually increases for the whole scene! But let's not confuse ambient light with reflected light. They are VERY different in factoring this. You are right if there is ambient light always present, you will hit a point where you cannot see black getting any blacker anymore. At this point there is no gain by closing the aperture futher. But that is very different to reflected light. Consider a fade to black scene. That would be super black in a room with no ambient light yet still suffer from reflected light.
Quote:
as long as room reflections aren't an issue. otherwise high bulb = brighter image = more light reflected back on screen = worse contrast

I think you are confusing on/off contrast and ANSI contrast. A room primarily affects ANSI contrast, not on/off measurements. A poor room will affect a scene with mixed content much more because adding 10 lumens to a bit of the scene that is meant to be 1 lumen is very noticeable, but adding 10 lumens to a bit of the scene that is meant to be 500 lumens, is not so noticeable. BUt that isn't on/off contrast. That is ANSI contrast or intrascene contrast.
Quote:
is it ever possible for this to not actually be the best contrast? is there a point where closing down the iris simply doesn't make blacks any blacker anymore? and if the picture is bright enough at this point, should this be where you stop?

By your example, yes if there is ambient light. If the room has no ambient light, then even if the walls are white, -15 will ALWAYS be better than -12.
post #4251 of 4435
Quote:
Originally Posted by JonStatt View Post

It is proportional. If you have double the light output, you will have doubled the reflections. It won't affect the on/off contrast as all you have done is lift black and white proportionally.
Well shining a flashlight raises the white level too as the amount of light you see from seated actually increases for the whole scene! But let's not confuse ambient light with reflected light. They are VERY different in factoring this. You are right if there is ambient light always present, you will hit a point where you cannot see black getting any blacker anymore. At this point there is no gain by closing the aperture futher. But that is very different to reflected light. Consider a fade to black scene. That would be super black in a room with no ambient light yet still suffer from reflected light.
I think you are confusing on/off contrast and ANSI contrast. A room primarily affects ANSI contrast, not on/off measurements. A poor room will affect a scene with mixed content much more because adding 10 lumens to a bit of the scene that is meant to be 1 lumen is very noticeable, but adding 10 lumens to a bit of the scene that is meant to be 500 lumens, is not so noticeable. BUt that isn't on/off contrast. That is ANSI contrast or intrascene contrast.
By your example, yes if there is ambient light. If the room has no ambient light, then even if the walls are white, -15 will ALWAYS be better than -12.

thanks this helps a bit.

i know there's a very strong relationship between room and screen, and the difference between on/off contrast and ansi contrast. just don't have the experience to put any of that theory into reasonable real world experience.

my concern is that inbetween stuff. i don't care how black my black bars are when the screen is super bright, it will always look black in comparison for me. but with dark scenes, that aren't 0IRE patterns, that's where i want to focus and get the best possible contrast/picture. it seems a little tricky because it's related to both on/off and ansi contrast. that is if my room were REALLY bad, even a dark scene would raise the black level with reflections.

i think maybe i'm trying to separate the effect of the room and the effect of the projector a little too much, and looking at things in too much of a theoretical way. i'm happy with my current settings, and i'm sure painting the ceiling will help further. guess i'll just have to play around a bit and try some experimentation instead of researching my thesis paper, haha wink.gif
post #4252 of 4435
I know i'm not gonna make a lot of friends with this post, but I just spent about 30-40mins playing the iris, lamp mode, gamma, contrast, brightness and a mix of test signals and actual video content.

in short the end result is my bulb set to low(only due to sound though) and my iris fully opened up.

I will preface the rest by saying everything is done by eye, and therefore should be taken as an example of what I can see, not what the projector can do.

no matter what I adjusted, I just could not see a closed iris making the picture anything other than dim. I was not able to get darker blacks, or more shadow detail without giving up at least as much on the white end. that is to say, while closing down the iris did lower my black floor a noticeable amount, it also lowered my peak whites a drastic amount. normally I would gladly give up brightness for blacks, but in this case I found the blacks to be just fine, and the extra brightness of more benefit. with dark, bright, and mixed scenes the image looked better and showed more detail with the iris fully opened. while i'm skeptical of the on/off contrast really being an improvement(I think as the blacks got better the whites got equally worse, therefore no improvement overall), i'm positive the ansi contrast is much better with the iris open. even with test patterns, there seemed to be an improvement in detail just above black, detail that could only be retrieved by adjusting the brightness setting up a notch, which also brought up the whole black level considerably.

I even went into high lamp mode with a closed down iris and I just couldn't see it. i'd much prefer the low lamp open iris to high lamp closed iris. it was too difficult for me to try and match relative brightness though, and the high lamp closed iris was a darker image overall. high lamp, open iris looked very good to me with content. only with a 0IRE screen did it leave me wanting.

so here's where i'm stuck at now. for a 0IRE screen(and don't think fade to black, because my eyes don't seem to adjust quickly enough) the closed iris, and low lamp mode give me the best black level. it's damn near approaching the best plasmas I've seen. if I hold my hand in the way, it's a very faint shadow, and it takes my eyes a good 10-15seconds of adjusting to the dark to be able to see that shadow, meaning for anything quicker than say 5 seconds(ie, fade to black between scenes), it is effectively black to my eyes. for every other situation, overall dark scenes, bright scenes, dark scenes with a single bright area, half dark half bright, they all look better with the iris opened up.

again, I want to remind everyone my comments are more about how I see, not necessarily what the projector does.

I will also end this with the statement that I realize adjusting just the basic settings may not be enough to take full advantage. I am by no means a pro calibrator or even a serious diy'er. at best an 'enthusiast' with a handful of calibration discs and a blue filter, haha. i'm also not trained or experienced with fully calibrated displays. part of the reason I preferred the brighter image was the greater 'steps' between black and just above black. for example high bulb, open iris I could see the difference between 16 and 17 and 18 clearly. low bulb closed iris it was near impossible to see the 'steps' until around 19 or 20, there was a hint that something was there in the 17 and 18 range, but no definition. I understand that more gradual steps should actually be better, I hate that 'digital' look of overly compressed video where you don't get a good transition in the shadows, but low bulb closed down was too little I think. the only way I could see information in the 17-18 range was to raise the brightness, which made 16 and 'black' too bright. the low bulb open iris was a good middle ground for me. I could see definition in the signal just above black without it looking like a definitive leap in brightness. when viewing the gradiants they looked smooth as silk.

so, correct or not, I don't know, but it felt like I was getting 'black crush' symptoms with the iris closed down, not an increase in shadow detail or contrast. not even with the high lamp mode to make up for the lost brightness.

again, I can't over state this. i'm not arguing the theory or the experiences of other ppl. what has been explained in this thread makes sense in theory, and can probably be backed up by measurements and observations of ppl with better/different vision than mine. I just wanted to put my experience and observation out there in case others had a similar experience and 'fixed' it, or others have the same experience in the future and go nuts trying to 'fix it'.

so again, thank you guys very much for the time and great explanations. it appears unfortunately I can no take advantage of the science due to my eyes, room, screen, or preferences(or maybe all of them?)
post #4253 of 4435
turning a room into a pit is the best to realize the benefits of the lower iris settings, especially on the models with the dual iris.

The ceiling grid and a few remaining tiles was my last part to black out in this photo.

blackout.jpg

I'm standing 6 feet behind the seats in this photo. The seating is only 14 feet from the 142" HP screen which looks quite large at this seating distance.

blackout1.jpg

Now it looks like the image is floating in space, I can't see anything on the side, top or bottom. With no light scatter, low APL scenes look as good as they are going to get.

The caveat of a darkened room is that is quickly exposes projectors that have a weak black floor or rely heavily on a DI.
post #4254 of 4435
Quote:
Originally Posted by zombie10k View Post


Now it looks like the image is floating in space, I can't see anything on the side, top or bottom. With no light scatter, low APL scenes look as good as they are going to get.

The caveat of a darkened room is that is quickly exposes projectors that have a weak black floor or rely heavily on a DI.

a few months ago, I was going crazy trying to figure out what I could paint in order to make my projector watchable. in the end I rightfully decided an upgrade was the only way.

but your bang on with the above statement. i'd like to darken my room until the screen is the only thing that get my attention. I can quite easily read by the light reflected off the screen, off the room right now. i'm anxious to see how much the ceiling helps. I won't be able to do much with the rest of the room, but when I get to start with a dedicated room, it'll be nice to know if I need to go all black, or how much color I can mix in to make it a little more aesthetically pleasing with the lights on.

on the other hand, you bring up another point that worries me. the 'honeymoon' is already over with the jvc. I still love it, but I see room for improvement. i'd hate to get my room so dark that a 0IRE image can be easily seen on screen again. I think i'd be a little weird to have to use bias lighting with a projector set up, but I guess it'd work just as well
post #4255 of 4435
Quote:
Originally Posted by fierce_gt View Post

a few months ago, I was going crazy trying to figure out what I could paint in order to make my projector watchable. in the end I rightfully decided an upgrade was the only way.

but your bang on with the above statement. i'd like to darken my room until the screen is the only thing that get my attention. I can quite easily read by the light reflected off the screen, off the room right now. i'm anxious to see how much the ceiling helps. I won't be able to do much with the rest of the room, but when I get to start with a dedicated room, it'll be nice to know if I need to go all black, or how much color I can mix in to make it a little more aesthetically pleasing with the lights on.

on the other hand, you bring up another point that worries me. the 'honeymoon' is already over with the jvc. I still love it, but I see room for improvement. i'd hate to get my room so dark that a 0IRE image can be easily seen on screen again. I think i'd be a little weird to have to use bias lighting with a projector set up, but I guess it'd work just as well

Firstly, I can see you were a little concerned about how you are coming across to other forum members. You have clearly been respectful, considerate of others opinions, and honestly asking the right and interesting questions. So rest assured it has all been good quality discussion.

Secondly, the science comes second to your own eyes! If you are happy with what you see, then nobody here should be telling you otherwise! I can't necessarily rationalize your findings. They do go against the general trend, but like I said, it's what makes you happy. The only "thing" I came up with is that white balance and gamma does change a bit when you close down the aperture. It is possible that what you need is a full calibration with the aperture at say -8. As this is a central point, it means if you play with the aperture either way you are not deviating too much. But it might allow you to re-evaluate the benefits of the aperture adjustment.

Also, ANSI contrast IS better wide open. ANSI contrast is very hard to measure properly, but I believe although its better, its within about 10% range fully open to closed on the RS45. The difference, possible due to the dual aperture is less with the higher models. But as I am very reluctant to trust ANSI measurements as it is SO hard to get right, and I cannot measure it myself, I have no absolute basis for this. However, the trend has always been that ANSI is better wide open while On/Off is substantially better closed down. The follow-on is that on/off is more important to most. To your viewing preferences, maybe you are seeing the small differences in ANSI and locking onto that factor....especially as you tried high bulb, aperture closed.

Ambient light elimination is THE most important thing to eliminate. White walls and ceilings come next, but you can still appreciate the on/off contrast range in this scenario particularly for fade to black scenes etc where you will of course see the inky blacks the projector is capable of. I do not have an optimal room....wife control in effect. The walls are light and so are the ceilings but I used a supermatte paint which helps reduce the reflections. Secondly I have a grey screen material which rejects some of the reflected light as it approaches off-axis. (This is also why my screen material retains some polarization meaning I MUST use horizontally polarized 3D glasses). The end result is that each time I Have upgraded the projector I can still see the improvement. I have had an RS1, HD990, X7, X70 and X75 (I haven't been some nutter upgrading each year as it may look from this.....long story for another time). But the point is I can see the contrast improvement in every model. For some reason the X75 I have now is over-performing according to the contrast measurements I am taking. The X70 had slight light corners and the X75 has absolutely none which is very fortunate (just luck of the draw with this). I run the aperture at -12 and I have a smaller screensize at about 80". Grey screen materials also have a tendency for lower than unity gain. -15 on an X75 or X95 is VERY difficult to achieve for almost anyone though as the dual aperture mechanism means light output is very low at this setting.
post #4256 of 4435
Quote:
Originally Posted by JonStatt View Post



So before you buy any more glasses, wait until you get the AG2 to test your screen material. Display a white screen, and tilt your head to the side while wearing the glasses (they do not have to be switched on for this). If the image goes dimmer when you tilt your head, you are out of luck, you will have to stick with JVC glasses. If the image does not go dimmer when you tilt your head, then you can buy other glasses.

Thanks,

I tried it and the image does NOT go dimmer when i tilt my head.
what does it mean? i can get any IR glasses now?
post #4257 of 4435
Quote:
Originally Posted by JonStatt View Post

Firstly, I can see you were a little concerned about how you are coming across to other forum members. You have clearly been respectful, considerate of others opinions, and honestly asking the right and interesting questions. So rest assured it has all been good quality discussion.

Secondly, the science comes second to your own eyes! If you are happy with what you see, then nobody here should be telling you otherwise! I can't necessarily rationalize your findings. They do go against the general trend, but like I said, it's what makes you happy. The only "thing" I came up with is that white balance and gamma does change a bit when you close down the aperture. It is possible that what you need is a full calibration with the aperture at say -8. As this is a central point, it means if you play with the aperture either way you are not deviating too much. But it might allow you to re-evaluate the benefits of the aperture adjustment.

Also, ANSI contrast IS better wide open. ANSI contrast is very hard to measure properly, but I believe although its better, its within about 10% range fully open to closed on the RS45. The difference, possible due to the dual aperture is less with the higher models. But as I am very reluctant to trust ANSI measurements as it is SO hard to get right, and I cannot measure it myself, I have no absolute basis for this. However, the trend has always been that ANSI is better wide open while On/Off is substantially better closed down. The follow-on is that on/off is more important to most. To your viewing preferences, maybe you are seeing the small differences in ANSI and locking onto that factor....especially as you tried high bulb, aperture closed.

Ambient light elimination is THE most important thing to eliminate. White walls and ceilings come next, but you can still appreciate the on/off contrast range in this scenario particularly for fade to black scenes etc where you will of course see the inky blacks the projector is capable of. I do not have an optimal room....wife control in effect. The walls are light and so are the ceilings but I used a supermatte paint which helps reduce the reflections. Secondly I have a grey screen material which rejects some of the reflected light as it approaches off-axis. (This is also why my screen material retains some polarization meaning I MUST use horizontally polarized 3D glasses). The end result is that each time I Have upgraded the projector I can still see the improvement. I have had an RS1, HD990, X7, X70 and X75 (I haven't been some nutter upgrading each year as it may look from this.....long story for another time). But the point is I can see the contrast improvement in every model. For some reason the X75 I have now is over-performing according to the contrast measurements I am taking. The X70 had slight light corners and the X75 has absolutely none which is very fortunate (just luck of the draw with this). I run the aperture at -12 and I have a smaller screensize at about 80". Grey screen materials also have a tendency for lower than unity gain. -15 on an X75 or X95 is VERY difficult to achieve for almost anyone though as the dual aperture mechanism means light output is very low at this setting.

much appreciated.
I think at the very least I've learned a lot, and now I know to look for these benefits when doing calibrations. whether or not i'm able to see them, who knows. but at least i'll try. i'll have another go after painting the ceiling just in case, but I suspect you are right that I probably need full calibrations at each setting to get full benefits. kind of like how I always hated the 'warm' color settings until I got into more detail with CMS. with factory presets I prefer a less warm color setting, but after calibration I did find it more natural.

I would agree, the first time I saw a quick fade to black with the jvc I was inspired! it may not be perfect black, but it's definitely 'good enough' that i'm worried about other things for now. thanks again
post #4258 of 4435
Quote:
Originally Posted by fierce_gt View Post

I would agree, the first time I saw a quick fade to black with the jvc I was inspired! it may not be perfect black, but it's definitely 'good enough' that i'm worried about other things for now. thanks again
Agreed.

I was a CRT holdout until this time last year. The older JVCs were good, but not quite good enough to make me part ways with my good old CRT. With gamma boost, CRT can do near-perfect blacks. Full-fade-to-black-can't-see-your-hand-in-front-of-your-face-blacks. Massive on/off that puts even the best digitals to shame. You know the opening scene in Cars when Lightning is dreaming in his truck? With my CRT, it literally looked like the system was powered off. It blew digital projector guys' minds when they saw it. I loved that, so I was very worried about not being happy with with any digital replacement. Still, I had a bunch of reasons to switch.

The RS45 was the first digital in my price range with very good blacks, a "less digital" look to the picture, and enough other desirable attributes that the switch made sense to me. Even coming from CRT and being a nut for incredible blacks, I've been thrilled with the RS45. I didn't realize how much I was hating the noise, and the projector is essentially silent, even though it's on the ceiling only a few feet back.

I started out running with iris completely closed, low lamp, 96x54 ~1.3 gain screen, fully light-controlled room with fairly dark walls and floor. Not a bat cave, but pretty dark. I haven't measured the brightness lately, but I've opened up the iris only a couple of clicks, and I had some HT buddies over for to watch The Hobbit in 3D a month or so ago, and we didn't even use high lamp mode - just opened up the iris around half-way. I think I'm at around 400-some hours now. I probably just jinxed myself, but other than some HDMI issues which I can't pin down, I just wanted to say impressed I am with this projector.

Also, I totally agree with how important room/screen are to a projector's performance, and what a good room does to expose a lesser projector. After my CRT was gone, but before I'd ordered the JVC, I tried an Epson 8350 just for fun. While it looked pretty great in my buddy's non-fully-light-controlled multi-use room on a 10-foot 1.1-gain scope screen, it looked terrible in my room. Really terrible. With the projector displaying black and a Blu-ray blocking the lens, the light leak from the projector exhausts put more light on the screen than does the RS45 with picture mute on.

A fully light-controlled dark room is critically important to ANSI contrast, but absolutely does expose projectors with less-than-great blacks.

Cheers,
SC
post #4259 of 4435
Quote:
Originally Posted by JonStatt View Post

Firstly, I can see you were a little concerned about how you are coming across to other forum members. You have clearly been respectful, considerate of others opinions, and honestly asking the right and interesting questions. So rest assured it has all been good quality discussion.

Secondly, the science comes second to your own eyes! If you are happy with what you see, then nobody here should be telling you otherwise! I can't necessarily rationalize your findings. They do go against the general trend, but like I said, it's what makes you happy. The only "thing" I came up with is that white balance and gamma does change a bit when you close down the aperture. It is possible that what you need is a full calibration with the aperture at say -8. As this is a central point, it means if you play with the aperture either way you are not deviating too much. But it might allow you to re-evaluate the benefits of the aperture adjustment.
.

fierce_gt,

Agree with Jon here, you've been respectful and considerate, so no worries there smile.gif

As others have mentioned, your room could be having an impact on your evaluations. But it also might have to do with your PJ being mounted at close to its furthest throw. I can't remember for sure, but I think the iris related contrast improvements are more drastic for PJ's mounted at the shorter throw, as zooming the lens also has an effect on internal light scatter.
post #4260 of 4435
Quote:
Originally Posted by fleaman View Post

fierce_gt,

Agree with Jon here, you've been respectful and considerate, so no worries there smile.gif

As others have mentioned, your room could be having an impact on your evaluations. But it also might have to do with your PJ being mounted at close to its furthest throw. I can't remember for sure, but I think the iris related contrast improvements are more drastic for PJ's mounted at the shorter throw, as zooming the lens also has an effect on internal light scatter.

cool, I hope you're right about the throw. i'll give things another check when I paint the ceiling, but if I don't notice a huge improvement i'll assume that has something to do with it, and maybe i'll save myself some sleep, haha.

plus, sometimes it's good to leave yourself a little room for improvement. we all know what it's like getting some new gear, thinking it's amazing, and then slowly getting accustomed to it and craving more. it'll be a lot cheaper for me to close the iris than buy an x55 or x75 tongue.gif
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