Re: [APML] Film Tri-Color Filters?

[Chuck Vaughn <aa6g@aa6g.org>]

Roland,

I agree with Shekhar on this one.

The intensities (brightness) from each channel do not add. If you have
Photoshop, bring up the Color Picker. Play around with entering values
for RGB. Look at the corresponding HSB changes. The highest single RGB
value always determines the Brightness. The only way to get the hue at
the  crossover wavelength to be maximum brightness is for each of the
two channels to have the same level.

I think the idea of brightnesses adding is a holdover from tricolor
printing on real photographic paper but I have never done this. Maybe
Tony has some insight here.

The traditional idea that you want 50% transmission at the crossovers
for digital imaging is wrong. I need to get on the stick and update
my article about this. :-)

Chuck <aa6g@aa6g.org>

--------------------------------

>>>>>> "Shekhar" == Shekhar Borde <shekhar@prodigy.net> writes:
> 
> Shekhar> In short, adjacent filters need to *each* transmit 100%
> Shekhar> at the crossover points (as opposed to the popular 50%
> Shekhar> approach) and the crossover points should be around 490nm
> Shekhar> and 580nm.
> 
> What is your reasoning behind the 100% transmission of both filters at
> the crossover point?
> 
> If I consider a pair of hypothetical sources that emit at 490nm and
> 540nm and the same intensity, I will get the correct color but the
> wrong relative intensities.
> 
> roland


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