[FoRK] Breakthrogh in HDTV projector pricing

Brian Atkins brian at posthuman.com
Wed Jul 21 17:27:30 PDT 2004

Dave Long wrote:
>>I haven't read up much on the subject, but apparently the screen will 
>>only reflect back red, green, and blue wavelengths in very narrow bands 
>>and otherwise mostly absorbs other light. So if the projector's color 
>>wheel filters or whatever means it uses to generate RGB doesn't 
>>precisely match the screen characteristics it will not perform perfectly.
> I was under the impression that color
> encodings for broadcast were based on
> human eye response, which would imply
> everyone's projectors would be using
> the same RGB frequencies. *
> Are there economic (or legal) reasons
> to use different sets of primaries?
> -Dave
> * NTSC, PAL/SECAM, and SMPTE look like
> they pretty much agree on R,B,W, with
> only NTSC G showing much variation.

The standards are beside the point in this case. No matter which 
standard you use, the image has to be physically reproduced in the end 
using some mechanism. Various types of displays use differing 
technologies to do this, and depending on how they do it there may be 
differences in the particular RGB frequencies produced. You can of 
course tweak the RGB light intensities to make the output of two 
different projectors look nearly identical to the human eye, but if we 
are dealing with a screen that only will properly reflect frequencies in 
very narrow gaps then those two projectors may perform quite differently 
when used with that screen.

We'll just have to wait for more details. It may be that it works great 
with pretty much all projectors.

I guess the ultimate evolution would be to have a projector that 
produces extremely narrow RGB wavelengths (laser-based presumably) and a 
matching screen for best performance. Such a combo could absorb nearly 
100% of ambient light giving really great black levels. I know various 
companies including Sony are working on stuff like this.
Brian Atkins
Singularity Institute for Artificial Intelligence

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