Bit of a grey area eh Ken. 😎
Regards John Duggan, Wales, UK
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On Mon, 29/10/18, Ken Norton <ken@xxxxxxxxxxx> wrote:
Subject: Re: [OM] Tetrachromacy
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Date: Monday, 29 October, 2018, 18:33
> It’s interesting to me
because I lecture on vision as part of my job, and to day
I’ve spoken only about rods and cones (and photo-sensitive
ganglion cells), never about the 3-colour properties of most
people’s cone cells. And now I know that there are
people with 4-colour cells.
Several years ago I did quite a bit of research
into this. The people
with four-color (not
colour) cones are rare enough to not be
considered part of the normal human race. :)
HOWEVER, there are
people who have rods with
some pigment.
It's
pretty fascinating that the human eye does not actually
"see"
red. The red cones see a
wide band of color from red down to yellow.
This band is overlapped by the green cones. To
determine "red", the
human vision
system sees the absence of green. So if the eye sees
green and red, it's actually yellow/orange.
If it sees red but not
green, then it's
actually red.
This is very
different than most digital sensors that traditionally
have had pretty narrow-band filters with little
overlap between blue,
green and red sensels.
Canon sensors are very wide-band with a thin
pigment. The color accuracy is secondary to
dynamic range. Color is
determined by the
same method as the human eye - using
"mix-minus"
calculations. (done
on-chip at time of exposure, pre-raw). The Kodak
sensors used a very deep filter that preserved
color accuracy, but at
the expense of
bit-depth and sensitivity.
Not much of that matters to me at the moment.
Everything is monochrome
in Alaska now.
AG Schnozz
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