Backlit Screen - Huge Black level improvement. Full Fade To Black Video Inside!!! - AVS Forum
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post #1 of 16 Old 07-15-2010, 02:44 AM - Thread Starter
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I've mentioned my back lit screen on the CRT forum a few times, but only now have I been able to demonstrate the difference in black level with my Optoma H79 on my super high gain curved silver screen with the back light on vs off.

The animated gif video below starts off with a full fade to black at 9'2" diagonal and after a few seconds you will see the back light come on and see how much darker the absolute black looks.



Just thought I'd share now that I'm able to. Any opinions or comments?
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post #2 of 16 Old 07-15-2010, 02:54 AM
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Quote:
Originally Posted by MTyson View Post

I've mentioned my back lit screen on the CRT forum a few times, but only now have I been able to demonstrate the difference in black level with my Optoma H79 on my super high gain curved silver screen with the back light on vs off.

The animated gif video below starts off with a full fade to black at 9'2" diagonal and after a few seconds you will see the back light come on and see how much darker the absolute black looks.



Just thought I'd share now that I'm able to. Any opinions or comments?

Adding light in the room cannot reduce the black level, but may alter how you are perceiving that black level. Remember, humans are not relevant to the basic physics involved.

"What we do in life echoes in eternity." General Maximus Decimus Meridius
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post #3 of 16 Old 07-15-2010, 03:11 AM - Thread Starter
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Originally Posted by 18628239 View Post

Adding light in the room cannot reduce the black level, but may alter how you are perceiving that black level. Remember, humans are not relevant to the basic physics involved.

Obviously it doesn't reduce light output. It's perception, but perception can be everything...it is very real though. The human eyes are equipped with our very own dynamic irises just like the current crop of LCD projectors, only far more advanced. If you have ever come in from a bright sunny day to a much dimmer room take note of how dim the room is before you eyes adjust. Usually your irises act so fast you can barely tell you have them, but in extreme cases your eyes adjust slower and you can tell if you take notice.

During a long very dark scene or fade to black normally your eyes' irises would open up wider and wider allowing more and more light in. The longer the dark scene or fade to black is the brighter the darkest black will appear because your eyes are adjusting more and more. The back lighting forces your irises to close down during these types of scenes/fade to blacks so your eyes will not allow more light in during such dark scenes/fade to blacks....thus you take in less light and see a much darker blacker black.

The effect should actually be better with a blue, green or white light. Red has less of an effect on the irises than those. I'm considering giving blue a try.
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post #4 of 16 Old 07-15-2010, 04:38 AM
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I remember reading about this back when samsung came out with the last of the led dlp's. I think people were putting some kind of back light or light box full spectrum to enhance the led colors on the screen? Not sure if this is the same thing or if it would work for projectors.
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post #5 of 16 Old 07-15-2010, 11:34 AM
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my theater room with an iphone 3gs



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post #6 of 16 Old 07-15-2010, 12:18 PM
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While back lighting can improve perceived black level it can also lower your real contrast ratio. Get a sensor and see what even the slightest amount of light in the room does to your CR. With TV's 6500K back lighting is amazing but with a tv you cannot lower your CR by using back lighting. I did some trials on back lighting with front projection and while there was a definite bonus with absolute BL as soon as I saw what it was doing to my 'real world' CR I instantly stopped my testing. Now if a Dynamic Back light could be fashioned that was fast enough to respond to what was being projected on the screen then we might have something (patent pending ).

Jason
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post #7 of 16 Old 07-15-2010, 12:52 PM - Thread Starter
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Originally Posted by DaGamePimp View Post

While back lighting can improve perceived black level it can also lower your real contrast ratio. Get a sensor and see what even the slightest amount of light in the room does to your CR. With TV's 6500K back lighting is amazing but with a tv you cannot lower your CR by using back lighting. I did some trials on back lighting with front projection and while there was a definite bonus with absolute BL as soon as I saw what it was doing to my 'real world' CR I instantly stopped my testing. Now if a Dynamic Back light could be fashioned that was fast enough to respond to what was being projected on the screen then we might have something (patent pending ).

Jason

I tried the back lighting with a white screen and it simply does not work in a room with white walls. It caused black washout instead and gave a red cast to the image (especially blacks). However, I use a very high gain torus screen and it already rejects ambient light very well, so there is no cast or anything to the image, not even a fade to black. If it lowers the contrast ratio it is to a very minute degree, yet you still perceive many times the contrast due to the black level being many times darker to the eye.
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post #8 of 16 Old 07-15-2010, 12:59 PM
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This reminds me the Philips Ambilight development
http://www.research.philips.com/tech...ght/index.html
"You could describe Ambilight as a TV with built-in ambient lighting effects. But that doesn’t come anywhere close to the Ambilight experience – which is unique to Philips. Think of the difference surround sound makes and then consider Ambilight as the ‘surround color’ version. It completely immerses you in the action, makes the screen seem larger and relaxes your eyes. Even leading industry reviewers familiar with the whole gamut of new TV technologies are impressed."
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post #9 of 16 Old 07-15-2010, 01:15 PM
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sounds like a lot more effort than sunglasses.
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post #10 of 16 Old 07-15-2010, 06:59 PM - Thread Starter
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Originally Posted by newmember1 View Post

sounds like a lot more effort than sunglasses.

Obviously, but a much greater and real effect on perceived contrast, a much better looking black level and the whole image doesn't look dimmer. Also, you don't have to wear sunglasses with the lights off and look like someone trying to be super cool.
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post #11 of 16 Old 07-16-2010, 12:44 AM - Thread Starter
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Originally Posted by Verge2 View Post

my theater room with an iphone 3gs




I don't see anything but a black image.
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post #12 of 16 Old 07-16-2010, 07:33 AM
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Quote:
Originally Posted by MTyson View Post

I don't see anything but a black image.




You are catching on.
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post #13 of 16 Old 07-16-2010, 07:46 AM
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^ I like the shade of black you chose...
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post #14 of 16 Old 07-16-2010, 09:06 AM
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Originally Posted by TF Ghost View Post

^ I like the shade of black you chose...


No that's an actual fade to black picture in my home theater room, taken with a iphone 3gs. It's so dark the iphone cannot even register anything.


Basically i'm saying, screw led lights.
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post #15 of 16 Old 07-16-2010, 10:09 AM
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Quote:
Originally Posted by Verge2 View Post

No that's an actual fade to black picture in my home theater room, taken with a iphone 3gs. It's so dark the iphone cannot even register anything.


Basically i'm saying, screw led lights.

I'm not sure you understand. What I'm saying is it looks nice. You made a wise choice choosing a dark shade of black.
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post #16 of 16 Old 07-16-2010, 12:21 PM - Thread Starter
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Quote:
Originally Posted by Verge2 View Post

No that's an actual fade to black picture in my home theater room, taken with a iphone 3gs. It's so dark the iphone cannot even register anything.


Basically i'm saying, screw led lights.

Yeah, that just means your camera has a poor and small sensor, unless you are using a CRT projector, which wouldn't register with any camera or the human eye. lol. The human eye is far more sensitive than either of our cameras when it comes to seeing a fade to black.

BTW, for the record....I had to bump up the brightness about 20-30 points to keep it from recording a solid black image like you did. For the camera to see a fade to black the way my own eyes did at the correct brightness setting I had to bump it up to the point where it was a very bright medium gray. Recording a pitch black image is not reality though, so that is pointless if I took it and said "Look! My fade to black is so dark my camera can't register anything! Wow...that is so black!"......All that means is the camera's sensor sensitivity sucks compared to the human eye's sensitivity. Obviously, that would be a ridiculous test if I showed a totally black image without back lighting that is not representing the reality of what I see compared to with the LED lights being used.

The point here was to show a real world difference, not prove that a camera with a can't see a fade to black at the correct brightness setting because it has a poor sensor compared to the human eye. Both blacks would end up looking near equal except one without lights in the shot. Again, not reality. Not saying you have to use LED lights, but some find tests like this to be interesting.
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