[Red Brian]

A white surface reflects all light and a black surface reflects no light.


If I'm watching a black cow in a snowstorm then the projector is sending as much light as it can for the snow and no light for the cow? So the black cow would be the color of the white screen in dim light, hence the need for light control??


Why do movie theaters use white screens and not gray screens (hence improving black level at the expense of whites).


The rumoured new black screen sounds cool but it has no phosphors like a CRT so how does it do white? Multiple layers and something to do with reflecting light off the upper layers but being black underneath perhaps??


[This message has been edited by Red Brian (edited 08-16-2001).]

 

[Morbius]

Quote:

Originally posted by Red Brian: A white surface reflects all light and a black surface reflects no light. If I'm watching a black cow in a snowstorm then the projector is sending as much light as it can for the snow and no light for the cow? So the black cow would be the color of the white screen in dim light, hence the need for light control??

Yes - if you have a black cow - the projector is not

throwing light at the cow's image. However, there is

ambient light, and light from other areas of the screen

such as the white snow which bounce around the room and

may land on you black cow. If you could measure the light

from the black cow - it would be the color of a white

screen in dim light.


However, in comparison to the bright white areas of the

screen - the black cow is dark. Remember your eyes are

always adjusting for the present amount of light.


Quote:

Why do movie theaters use white screens and not gray screens (hence improving black level at the expense of whites).

Gray screens help improve contrast. Film and lamp

technology does not have a contrast problem - so they

use white. You use white for a CRT projector too.

When you have a digital projector that needs more contrast-

you use the gray screen.

Quote:

The rumoured new black screen sounds cool but it has no phosphors like a CRT so how does it do white? Multiple layers and something to do with reflecting light off the upper layers but being black underneath perhaps?? [This message has been edited by Red Brian (edited 08-16-2001).]

[/b][/quote]


Greg

 

[JimNiki]

I take it even film has a degree of leakage through the black (cow) area of the celluloid. One of the reasons why dlp's are so good at black levels is because the MDM's actually pivot to redirect the light away from the screen. In theory, no light from a dlp should be shing on the black (cow) area of the screen. (apart from ambient room light).


This is a fantastic fix for black levels! If only the bloody things had good resolution for a reasonable price!

(Not to mention, more rainbows than "Wizard of OZ").


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Tertiary adjunct to Unimatrix Zero-One


[This message has been edited by JimNiki (edited 08-17-2001).]

 

[Morbius]

Jim,


Even DLPs can have problems with black levels.


I recall a discussion a while back when a JVC press release

quoted that a new chip had 1000:1 contrast ratio, but JVC's

Tom Stites said that any projector that incorporates it

won't have a 1000:1 contrast ratio - because there's more

to the optical design than that.


Even though the DLP pivots the mirror to direct light away

from the screen - it has to go somewhere. It has to be

absorbed inside the projector. But the inside of the

projector isn't perfectly black - nothing is. So this light

can internally reflect inside the optical block and end up

finding its way out anyway - albeit at a reduced level.


Anytime you have to "dump" the light to create black - you

can have this type of problem.


The only way you really get black - is not to make the light

at all - which is what a CRT does.


Dr. Gregory Greenman

Physicist

 

[Ereiamjh]

According to Yamaha, they have a new color wheel which is different from all previous dlp color wheels. Instead of having an additional section of the wheel being clear for enhancing brightness for business use frt projectors, they eliminate this section and the entire wheel is dedicated to RGB. This, according to yamaha increases black level. Also the rate of spin is faster and this supposedly reduces rainbows. Now, I am just a novice, but I saw the DPX-1 today and I was impressed. I saw a $30k crt about 6 months ago and this dpx-1 seemed close. But it has been 6 months and I am a novice. But I did not see any rainbows. You can see more about it at yamaha's website.

Dan

 

[JimNiki]

I'm still waiting for the Epson (or was it HP?) who developed the new inkjet projection system with "Richer Blacks" and much more vibrant colors! Apparently the projector costs bugger all, but the 3x 44gl of ink (RGB) costs thousands per month! I knew it was too good to be true. (Should that have been CMYK inks?)


Seriously though, I thought that CRT's projected a black light to get such good black levels..... (NOT!)


(Sorry, I think there was a few bad blocks of ice in my bourbons)



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Tertiary adjunct to Unimatrix Zero-One