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Re: [OM] CCD image sensor cameras

Subject: Re: [OM] CCD image sensor cameras
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Tue, 7 Apr 2020 16:40:33 -0800
Mike (my eyes! my eyes!) Gordon wrote:
>  The color accuracy of a sensor has been theoretically quantified by the SMI

Yes. But there is a rub to that which Minolta discovered back when
they merged with Konica. Minolta's digital cameras were actually
highly color accurate, but the images not at all pleasing. Konica
brought "color theory" to the equation and made great leaps in making
the images "prettier". The transition was really apparent between the
A1 and A2. This is but one example.


>  The SMI varies depending on the illuminant and purportedly is independent of 
> the
> converter.  Sonnie tends to do well here with a denser CFA but truth  be told
> the measure in practice  is noisy above 80 and not very good at 
> discriminating the sensors.  Purples and true
> violets are notoriously difficult."

They are because purple is a combination of red and blue, but violet
is a color at the edge of the visual spectrum. The way to capture
purple/violet is to have the red sensels have a second sensitivity
bump down below 450nm. Kodak extends both the blue and red sensitivity
far below the normal cutoff and is deeper into the near-UV range. The
E-1 is the only digital camera I've tested that can accurately capture
an African Violet because it's a combination of violet, blue, and
near-IR. The E-1's IR cut filter is a blessing and curse because it
will accurately capture flowers (wedding photographer nightmares), but
will give magenta-colored blacks in some fabrics. The African Violet
is especially tough to capture.


> If one compares the spectral sensitivity of human cones (excluding 
> tetrachromats) vs a typical cam sensor one can anticipate it would be  
> difficult to devise a scheme where the two agree on color matches--so called 
> "Luther-Ives conditions."

I believe that this would be a fool's errand to try and get the
imaging system to match the human eye, because this would bias the
result in an unnatural way. This is no different than trying to adjust
an audio recording to correct for the "Fletcher Munson Curves". While
it seems like a good idea at the time, it really isn't. Because the
human hearing is adjusting for the losses and if you artificially
boost the levels to flatten the response curve then the mix sounds
tinny.

I think it is better for an imaging system to have native HSL curves
that better match desired outcome than a flat response. If the native
HSL curves of the sensor and pre-raw imaging chain are closer to the
final output - the level of correction required during conversion and
editing is much less. More editing/adjustment means less effective
bit-depth.

Honestly, I like my native images to be closer to Fujichrome Provia.
And the Kodak E-bodies do that.

AG Schnozz
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