I appreciate the analysis, although others may not. But to summarize... It is
the color filter?
As a former filter designer, I appreciate the effect of a sharper roll off
filter. So we are saying that it is the color filter creating the main
difference? And that the sensor, whether CMOS or CCD is just capturing photons.
That is, a less sharp filter will bleed a bit of one color into another color,
loosing color separation. Which can not be recovered in post processing the way
a shaper color filter would allow. If true, then different sensors will provide
a clear difference in an image, as discussed.
Are you also saying that the location of the color pixels helps separate the
colors? That is red and blue are further apart in wavelength, while green is in
the middle. I don't understand triangle separation.
If this is correct, that the difference is in the color filter, then there
could be CMOS sensors that achieve the same color separation/characteristics of
a Kodak CCD?
WayneS
At 4/6/2020 10:22 AM, Ken wrote:
>> Someone claimed, in the discussion, that it depends on the color filter of
>> the sensor. For CMOS sensors "...manufacturers broadened the light
>> transmission of the sensor filter to let more light in but weaken the color
>> differentiation."
>
>That is even more true with Canon sensors than the others. They biased
>towards light sensitivity than color sensitivity. In MOST cases, I
>think this solution is better behaved as it maintains a more accurate
>and usable gradient. But the problem comes in with color subtlety
>allowing for saturation adjustment.
>
>The analogy I like to use is comparing a hand-tinted B&W print with an
>actual color photograph. The Canon images are much closer to the
>hand-tinted print in theory and in practice. The image is actually a
>B&W images with color applied on top. While this is technically true
>with all digital camera images, the color information is weaker and
>will use a mix-minus algorithm to strengthen the color information,
>otherwise the bit-depth of the colors is too low. This is how the
>human vision system also works. We actually cannot "see" red. We see a
>color band that includes red. We also see green. (and blue). The human
>vision system determines whether or not something is actually "red"
>through the absence of green.
>
>Do I see Orange? Yes
>Do I see Green? No
>Subject is Red.
>
>Do I see Orange? Yes
>Do I see Green? Yes
>Subject is Orange or Yellow
>Do I see Blue? No
>Subject is Yellow.
>
>Raw image conversion must use this same type of algorithm in order to
>exaggerate the color bit depth. If each sensel (pixel) position on an
>camera sensor is only 50% dense (color density - 100% would let in
>zero light that isn't that color), then the bit depth of the color
>information is cut in half. This color information has to be made up
>somewhere else. Mix-minus is a way to recover some of that bit depth.
>
>Regardless of how the color information is derived, during the raw
>conversion process, it is generally applied after the brightness value
>has been determined. Which is also why there are two greens to every
>one blue and red. It has nothing to do with sensitivity, etc., it has
>to do with the triangle intersection of three pixels. With the
>exception of the Olympus CCD sensors (as well as several other cameras
>using Kodak sensors), raw conversion uses THREE pixels, not FOUR! The
>quickest way to determine if the converter has to use four is whether
>there is a gray line at the intersection between two contrasting
>colors. Anyway, I digress.......
>
>When Phase One changed over from CCD to CMOS, they had to work closely
>with the sensor fab people to completely customize the filtration
>process as well as adjust the raw converter to correct for the
>different technologies. It took years to get CMOS to work right for
>Phase One.
>
>AG Schnozz
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