How to create .RGB/.BW file?

How to create .RGB/.BW file?

Post by Eric » Tue, 02 Jun 1998 04:00:00



Hi,
    Just wondering how to create or edit SGI's .rgb file or .bw in
windows 95.
Thanks in advance
Eric

 
 
 

1. RGB to BW, Inner details?

Hello,

I'm curios to know the fine details on this conversion.

I am aware of the Y weighting often used by software.
I do have a problem with this tho, it doesn't look right.

The formula basicly tell us that :
grey = .299*r + .587*g + .114*b

Full brightness blue = 11.4% red + 11.4% green +  11.4% blue

Now on any monitor I used blue images look *much* darker
after the conversion to BW.

But Shouldn't the RGB level with start with be linear?
And so the monitor adjust the level to make it so each componant express
equal brightness at equal voltage on the componant of the grill?
So we should use:
grey = .333*r + .333*g + .333*b

but in this case also the image luminance level change.
(The blue images look better, but green images look darker)

The RGB level seem to be un equaly weighted and non linear.
Both methode seem incomplete , well, wrong :)

If I wanted to do 'perfect' BW conversion for trinitron tubes, what are
the visual dynamic of the RGB componant?
My guess a separate non linear formula need to be apply to each componant?

In case I'm not interested in doing a convertion just for my screen, but
for the world.
What formula should be used in this case?

Thanks in advance for sharing your knowledge,

Stephan

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