the truth about black levels

Going to the movies is a social event - different experience. You are right too, going to the movies isn't as fun if you start being obsessed with image quality. Many people here have said their home theaters are actually better than the cinema.. and not just picture quality - sound, comfort, acoustics...cleanliness. So "as good as the movies" is an outdated standard, i think.

Once you start down the path of home theater owner and actually have the ability to improve the experience, it's hard not to chase better image quality. *perceived* black levels are a critical part of that improvement, increasing realism and constrast. At a certain very rare combination of source, settings, light and location, a home projector can throw an image with such clarity and contrast it stops being a movie and starts looking real. Even with the 4Ks, i've never had that "real" experience at a theater.

I own a projector with bad black levels. I made the following experiment:
- Set the zoom that not the whole screen is covered with the projected image.
- Start paint and to fill the whole drawing area with black.
- Now compare the black inside the drawing area with the "black" on the screen where no image is projected (this is the blackest black possible).
Because I have not an optimized room, but a normal living room with white ceiling and light colored walls, I could see no difference. The reflected light was strong enough that the projector has almost no influence on the black level.
But our perception works differently!
Do you believe that field A and B have exactly the same color?
http://www.cine4home.de/knowhow/kontrast_bei_digitalprojektoren/image006.gif

High contrast ratios and black levels not important at all in a normal living room. Don't waste your money!

You have an excellent understanding of it. There is an absolute possible black level that is obliterated by room reflection. wearing a white shirt could add another .002 FL :P So it's perceived contrast that matters.
A meter would tell you the absolute light levels, but we don't watch movies thru meters, we use eyes.

Really there's no black black enough, because eyes can change chemically over 30 minutes for a 1,000,000:1 contrast. The only thing that keeps blacks looking black is being adjacent to a much lighter value. It takes a lot more work, but if you can light a room so that light ends up everywhere BUT the screen, the image appears to have incredible contrast.

Think of it this way, people try so hard to get black walls, curtains, ceiling thinking that will give them the best image. And it's true a low-lumen projector in a totally black room will read the lowest absolute black levels and highest theoretical contrast. The problem is the screen is now the whitest (or lightest grey) surface in the room, and will always appear lighter. The worst thing you could do is put a nice black border around a screen to show just how grey the screen is compared to pure black, but that is exactly what everyone does. It's counterproductive.
I've been working to create a room balanced to be between the screens darkest and lightest grays (black and white to the eyes) People are more confortable not sitting in the dark, eye fatigue seems less and the image looks incredible. But it takes a lot of work and isn't practical for many.

All i'm suggesting is there's more to image quality than numbers from a colorimeter. I know that offends the purists but as long as our eyes are part of the system, dynamic effects should be part of the equation. Local color is actually more to do with physiology and psychology, but you can apply the concepts,
"After a great deal of research by Disney Imagineers and Kodak photography experts, the pavement in Epcot was painted a specific, custom pink color, in order to make the grass look greener and pictures look brighter."
Edited by DragonSixGolf - 11/1/12 at 9:11am

So is that why my W7000 looks better with a certain amount of ambient light? I notice when the room is a its lowest dimmed light setting or total darkness, the w7000 doesn't look all that great but if I set my dimmer just above the halfway dim, closer to full light, the W7000 looks spectacular, IMHO.

This thread has me thinking about getting rid of my frame, masking panels, and painting the front wall all light gray just like the screen. The one think I love about having the borders is the "screen" (painted wall) looks so impressive when the projector is off. Other than that, I have to admit it was nice back when I had a "floating screen" when the wall was all one color and I could use whatever size of screen I wanted.

Also, I could NEVER see the black bars above and below the screen on 2:35:1 movies, they do show up now on dark scenes.


Hmmm... I'll have to think about this....

right. i always noticed it coming back into the the room from a brighter area. Image looked very "punchy" Then, 10 minutes later...grey bars..muddy blacks. So ambient light is not the enemy, at least no to bright projectors. But beighter projectors produce their own ambient light, which is why reflection control matters.

Dynamic irises improve blacks my reducing the light from the projector.. a brighter room calibrates our own irises to do something similar. The trick is making sure the light reaches your eyes, but not the screen. As for the border, i actually suspend the screen away from the wall but this requires alignment almost to the pixel. it also allows backlighting but that approach has other issues so i don't recommend it.

here's a post where i give a simple example of what ambient light does to contrast but the next part would be adding enough light (to our eyes, not the screen) so that the new .6 level appears as the .1 Shadow detail is critical area where room lighting can easily overpower the faint differences in value.

coderguy gives a technical explanation much better than i ever could

the only problem is this is subjective.. so how would a calibrator deal with it? i would like to find out if there are explanations or guides for compensation lighting.
Edited by DragonSixGolf - 11/1/12 at 10:40am

Great post! I'm going to be spending quite some time thinking about this....

ive already tied my brain in knots with it. especially coderguys mention of the black floor. Theres always a certain minimum level of light from the projector on the screen. You can minimize it with blacked out walls etc but you can never get it below the projectors native black level. As seen from the checkerboard video, grey can look light or very dark depending on what it's next to. So the goal becomes make the grey look black by lightening everything else. The difficulty becomes doing this in way that doesn't obliterate shadow detail.

I'd like to try a dimmable lamp, with a precise mask that allows illumination of the wall, but not the screen mounted on it. i think this will give a very strong illusory effect similar to the video, where a white screen appears much darker than the gray wall behind.

i've also been thinking about a room with saw-tooth or coffered ceilings, columns and insets on the walls where every surface facing the screen is angled or faced in velvet, but every surface facing the viewer is light and neutral. It would probably look like a stealth fighter, but i;ve seen auditoriums with similar features (most likely to control sound reflection, not light)

Everyone does this, thick black felt or other light absorbing material. I find it hard to believe thousands of people on here are wrong

depends on why the border is there. I think it's to catch light spill from a less than perfectly aligned image.. do you agree? Some also like the finished appearance it offers - "picture needs a frame". In either of these cases would a white/lt. gray frame serve any purpose? no. So a black frame isn't there to improve the picture, just contain it. Have you noticed how easy it is to tell how unblack an image is next to a black border? what did you think of this videeo?

Any other border color other than black stands out to our eyes. So even though black may technically make the PJ's black next to the border appear brighter, the goal is you shouldn't see or notice any border at all while watching movies, that is the point of the black border (as well as to absorb overflow if you can't mount perfectly). Since you don't really see the border, you aren't able to compare it by eye so it does not have the negative effects discussed in this thread usually.

This is a very interesting topic! This is stuff I would never, never have thought about. It amazes me how the mind works. I think after reading this stuff I'm starting to become a changed believer.

Thanks for making me rethink what I thought was common belief or understanding. So this is what a religious awakening feels like. You guys are GODS!

Maybe someone can implement Philips's Ambilight technology for projector?

http://youtu.be/Zz2EjUWCqI4

but this is true only for a perfectly dark room, yes? in that case, a black border , white border, green border would all appear the same..dark and completely invisible. In a room with ambient light, the border is very visible, and becomes a distraction with the issues mentioned. Especially when putting the most light absorbing surface (velvet) against the most reflective one (the screen)

The ambient light approach is based on 2 simple observations:
1. in a perfectly dark room, with a projector showing an empty frame, the screen is the lightest surface receiving the most light in the room. We've all been disappointed staring at the grey box on the wall, at least until the movie starts. This is a technical limitation not easily fixed, except for CRT or very expensive projectors, DI, etc.

2. Our eyes our easily fooled. Even after knowing the two grays on the checkerboard are the exact same value, it's impossible to see them as such (at least for me)

Is there a way to use this effect to improve the perceived image quality? Especially because the vast majority of projectors (including mine) have average blacks and are viewed in less than optimal rooms. I've been amazed by the "floating window" effect a few times, but it was pure accident. I'd like to understand better how to achieve that effect more often.

You have much more technical and practical experience, but reconsider some assumptions about ideal viewing. You don;t think my approach has any merit?

I am not sure about backlit or bias lighting with projectors, I've heard mixed results, overall though the darker room is better even than a room modded with bias lighting. Generally you have to cover a room head to toe in black to get the best image or floating window effect (but that is not always easy to do).

I don't know in all situations as I've always had a black border or no border at all (once projected on a wall temporarily), but overall I think I'd prefer black in most cases.
In such scenarios even in a fully dark room, there is usually enough light coming off the screen even in a dark room for any border color other than pure black to be seen (and even black you can probably still see it if you really try).

wow, very impressive technical skill to make the lighting actually follow the video. But the effect is very distracting to me - cool for parties but not to improve the image. It has to be unnoticeable or the effect is lost. Still, active backlighting might be useful in some way. Interesting.

I think SI screen has an ambilight type screen:

http://vimeo.com/48770948

Just to clarify, i wasn't talking about using a color other than black as a border. i was just illustrating to uullddrr why no other color than black is used which i guess is confusing, even tho i'm agreeing with you. None of my screens have borders and are suspended away from the wall, which isolates the focus plane and ( i hope) helps the floating window effect. Going back to the checkerboard example, maybe thru light control the grey square surrounded by black (the screen) can appear darker than the same grey behind (the background).

i have experience with local color effects in print design but it is very different trying to employ simultaneous contrast with active lighting in 3D

I just epent a few hours reading about the SI screens and bias lighting. The SI screen is *exactly* what im trying to accomplish. An image with a lot of punch and perceived contrast in ambient light. The difference being instead of a selectively-engineered substrate, i'm using something closer to ray-tracing. If i had $4k i could save a lot of work if the screens lreallu look as impressive as the edited webshots I notice they also use bias lighting... but the bright blue halo is not the effect i'm after. I have in mind something like an evenly-lit frosted plexi or rear projection material wall in 10-30% gray, if active lighting at all. it certainly would making testing different values easy.

Anyway, i've been reading up on bias lighting and even metamerism... people have already done the research so all i have to do is understand it....these links have valuable information. read them if you can.

http://www.cinemaquestinc.com/ive.htm

http://biaslighting.blogspot.com/

this thread is more appropriate to the /display calibration forum unless you make the case theat cheap projectors with bad blacks are most in need of help
Edited by DragonSixGolf - 11/2/12 at 2:15am

I love the look of the new zero edge type screens.

Here is another video that really shows off the bias lighting.

So is that why my W7000 looks better with a certain amount of ambient light? I notice when the room is a its lowest dimmed light setting or total darkness, the w7000 doesn't look all that great but if I set my dimmer just above the halfway dim, closer to full light, the W7000 looks spectacular, IMHO.

Like this? This is pics of my BenQ W7000, which has quite poor native contrast. My screen is black velvet all the way around the screen area, side walls are treated in black velvet to the left of the screen but I haven't done the right wall yet. I have 3x50watt spotlights and in the 2nd image, 2 are directed at the floor (light beige carpet), slightly angled toward the viewing position and the other spotlight toward the side wall on the right. I agree, the image still looks great with ambient light. These are only photo's but you get the idea:

No, not like this. The goal is to increase the amount of light hitting your eyes (thus making your irises close more) without afflicting the image on the screen. The ambient light in your example is reflected back to the screen and washes out the image reducing contrast more than it gains by closing your irises.

That gives me an idea, what if we just put some light around our eyes, wouldn't that do the trick?

lol

Whats the deal with different color lighting? Purple, blue? Wouldn't you just want white?

I haven't read up on this, just thought it was odd the bias light in the video I posted was purple. Is there an optimal color to maximize the effect?

The optimal color would be WHITE of the same color temperature as the standard your display/PJ system is calibrated to. In case of Rec.709 it would be 6500K white.

I'm not sure if this is off topic but.....

a movie theatre projector has to fill a far bigger screen from a much longer distance so there are going to be trade offs in performance vs a home projector.

I find the mits hc500 showing a blu ray on my stewart screen to be far more detailed and pleasing than the theatre..... I find theatre to be less pop in colour/almost a grayish tinge.

I agree with others that going to the theatres is an experience and you have to shut off that Home Theatre part of your brain or else you spend your time obsessing over artifacts during fast action scenes or wondering how old the pj is and has anyone calibrated the damn thing.