Digital BW, The Print

on 2/7/02 1:57 AM, SKID Photography wrote:

>>>> What I took from my question to Austin (Horses Mouth, about a week ago) is
>>>> that these one shot cameras interpolate color, not detail.
>>>> 
>>> I do not understand how one can separate 'color' information and 'detail'?
>>> They are one and the same.  It's not like there are separate or different
>>> parts that make up the image.
>> 
>> Say your sensor is a grid of two sensors across by two down. In grayscale
>> mode you get a 4 pixel capture. You have 4 pixels of detail, represented by
>> one channel which has 4 pixels.
>> 
>> If the camera then applies an algorithm to give each of those pixels an RGB
>> component, that requires interpolation, and you'll end up 3 channels at 4
>> pixels each.
> 
> Stop right there and you have your answer.  INTERPOLATED INFORMATION!
> Not reality.  End of more real information.

Well, it depends on how literal we want to be. See, I think I'm correct in
an absolute sense, just not a practical sense. I not clear on how these
cameras work in grayscale, so I would forget anything I've said as it
relates to one shot cameras, but we could discuss this on a pure digital
science level (not that we should need to or want to), where I am
"technically" correct (to the best of my knowledge ;-)).

Let me just expound a bit, then we can continue, or drop it.

Above you asked how we can separate "color" from "detail" as they are one
and the same. Well we can and they're not. Austin used the right terms,
chrominance and luminance - they are different. Convert an RGB image to Lab
mode and you will have separated the two. The Luminance will live in the L
channel, and the chrominance in the a & b channels. look at each channel
individually. The L channel is a grayscale image which has virtually all the
detail, the a & B channels hold the color, and they are mush. So the context
in which I discussed "detail" is as it relates to luminance.

Then you say interpolation is the end of real information. That's true by
definition, but has no relevance to luminance, and "information" is a vague
term which I never used as it has not been defined. My point is that these
one shot cameras do record a luminance value at each sensor, thus detail,
and it is the chrominance which is interpolated.

The problem is that with the color filter on each sensor the luminance
(detail) values will be somewhat arbitrary at each pixel in a real world
imaging sense.

Todd