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Discussion Starter · #1 ·
Why is it that a little bit of ambient light will kill the contrast on a CRT projector but an equally bright digital (lets say 1000 lumens) can cut through that and still display a nice picture without a taking a ginormous hit to it's black levels?
 

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Because digital projector contrast black levels aren't as good to begin with (so they aren't hurt as much by ambient light) and they are so much brighter on the top end they have the power to cope with ambient light as well.
 

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Because high CRT lumen numbers are PEAK WHITE, not ANSI lumens. A 7" CRT is about 150 ANSI lumens and about 605-700 Peak White lumens while my 4805 DLP is about 600 ANSI lumens (no clue what peak white is). Also, its dark end is so much darker that it washes out much easier. To get a better ambient light image with CRT you have to raise contrast two points more or higher and elevate the black level (brightness).
 

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Discussion Starter · #4 ·
So what about black levels on a projector like the HD70 or HD1000U if there was a little ambient light coming in around my blackout curtains or a desklight on somewhere in the room? Is that light gonna kill my black levels and contrast despite the fact that they can supposedly perform alright in low ambient light situations?
 

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Quote:
Originally Posted by bkchurch /forum/post/0


So what about black levels on a projector like the HD70 or HD1000U if there was a little ambient light coming in around my blackout curtains or a desklight on somewhere in the room? Is that light gonna kill my black levels and contrast despite the fact that they can supposedly perform alright in low ambient light situations?


The bottom line is true black is going to look like what the screen looks like under whatever light is present in the room during that instant of viewing.


There is in fact a whole other thing that takes place and that happens in your eyes and brain and is influenced by the projectors CR and lumens and your screen color and gain. And that is how you perceive Black in terms of white and white in terms of black.


If you go to the below link and look at post #117 thru the end of the thread you will see photos and more explanation of this.

http://www.avsforum.com/avs-vb/showt...8&page=4&pp=30
 

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Quote:
Originally Posted by bkchurch /forum/post/0


So what about black levels on a projector like the HD70 or HD1000U if there was a little ambient light coming in around my blackout curtains or a desklight on somewhere in the room? Is that light gonna kill my black levels and contrast despite the fact that they can supposedly perform alright in low ambient light situations?


Your blacks will become the color of the screen, but it might be ok-pretty good contrast (depedning on the amount of light and the screen). If you want to maximize the ambient light picture use a grey screen and shade as much sunlight as possible. Also, try to shade indoor light to keep as much "hard" light off of the screen as possible.


In a room with a single shaded light and a grey screen the HD1000U can put out an impressive image. For the best amibent light image you gotta be clever and creative with your lighting.


Front projection performs best with SOFT ambient light.
 

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Quote:
Originally Posted by bkchurch /forum/post/0


Why is it that a little bit of ambient light will kill the contrast on a CRT projector but an equally bright digital (lets say 1000 lumens) can cut through that and still display a nice picture without a taking a ginormous hit to it's black levels?

One word: lumens.


But, there's a trade off so we are not out of the woods yet. One day...
 

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It also really depends on the content you're watching. For tv / sports, goosing the brightness will be fine, as this type of content is generally bright, and blacks will look ok because most of the contrast you're perceiving is instantaneous ( ANSI ), where your eyes are perceiving the blacks as black because they're comparing them to the bright parts of the same scene, and your eyes compensate for the elevated black levels.


For most movies, you'll be dissapointed in with anything but very moderate ambient light. This is because movies generally have at least some very dark scenes, where your eyes are very good at picking up how bad the blacks are due to the lack of lack of bright areas. Grey screens can help, but, it's just making something bad a bit better.


If it's tv / sports that you're concerned about, and you have the flexibility to table mount the HD1000 / HD70 you can use a retro-reflective screen to help reject ambient light, and get more light back to your eyes off the screen. If you ceiling mount, the effect is mitigated. If you have ambient light coming from behind you ( opposite the screen ), retro-reflectives are even worse. Retro-reflective screens also have a narrower high gain viewing cone than conventional screens. You basically have to be sitting directly in front of them ( not off to the side past the screen edge ) to get the advantage during daylight / ambient light viewing.


I have an HD1000 in a table mount / retro screen configuration and it works great for me for tv / sports during the day .. even 40' of windows and no blinds. What helps is a dark coloured screen wall ( mine is brick flanked by dark grey wood ).


Hope this helps,


Jonathan
 

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This thread will point out the importance of lumens in maintaining CR while subjected to increasing ambient light.

http://www.avsforum.com/avs-vb/showthread.php?t=743468


It's not the only method as jrwhite points out another method is to send ambient back to where it came from with a retro screen. Another is with a surface sheen, ambient from the sides can skip off the screen to the other side.
 

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Quote:
Originally Posted by jrwhite /forum/post/0


It also really depends on the content you're watching. For tv / sports, goosing the brightness will be fine, as this type of content is generally bright, and blacks will look ok because most of the contrast you're perceiving is instantaneous ( ANSI ), where your eyes are perceiving the blacks as black because they're comparing them to the bright parts of the same scene, and your eyes compensate for the elevated black levels.


For most movies, you'll be dissapointed in with anything but very moderate ambient light. This is because movies generally have at least some very dark scenes, where your eyes are very good at picking up how bad the blacks are due to the lack of lack of bright areas. Grey screens can help, but, it's just making something bad a bit better.


If it's tv / sports that you're concerned about, and you have the flexibility to table mount the HD1000 / HD70 you can use a retro-reflective screen to help reject ambient light, and get more light back to your eyes off the screen. If you ceiling mount, the effect is mitigated. If you have ambient light coming from behind you ( opposite the screen ), retro-reflectives are even worse. Retro-reflective screens also have a narrower high gain viewing cone than conventional screens. You basically have to be sitting directly in front of them ( not off to the side past the screen edge ) to get the advantage during daylight / ambient light viewing.


I have an HD1000 in a table mount / retro screen configuration and it works great for me for tv / sports during the day .. even 40' of windows and no blinds. What helps is a dark coloured screen wall ( mine is brick flanked by dark grey wood ).


Hope this helps,


Jonathan


Viewed content is very important and most of us want to watch a wide range of it. That's why I have always suggested an adjustable system that accommodates both darkened theater like movies and also bright sports bar images with beer drinking lighting up in the room. Most projectors also have several preprogram modes you can set up to make the at the projector adjustment.


If you need the best of both worlds one screen can do both jobs if the projector is selected correctly.
 

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Quote:
Originally Posted by bud16415 /forum/post/0


There is in fact a whole other thing that takes place and that happens in your eyes and brain and is influenced by the projectors CR and lumens and your screen color and gain. And that is how you perceive Black in terms of white and white in terms of black.

Whoops, missed that part of your post Bud. Sorry, didn't mean to restate.
 

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Quote:
Originally Posted by bud16415 /forum/post/0


This thread will point out the importance of lumens in maintaining CR while subjected to increasing ambient light.

http://www.avsforum.com/avs-vb/showthread.php?t=743468


It's not the only method as jrwhite points out another method is to send ambient back to where it came from with a retro screen. Another is with a surface sheen, ambient from the sides can skip off the screen to the other side.

I was being overly simple in my statement in an attempt to avoid the science and ensuing brain anurism.


My brief point was that although the HT PJ seems to have less quoted lumens, it has more than enough to help generate the CR needed for HT versus a "TYPICAL" business machine where lumens is most important and CR less important for data projection.


The human eye actually doesn't need more than about 100:1 CR for spot to spot contrast.


Obviously, a digital PJ is going to need lumens to create the needed grayscales. Just trying to keep it simple.
 
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