cyvideo
Veteran
My own opinion has changed over the years and currently I find myself leaning towards a bit more green (not too much) than magenta. And I'm sure that will change again.
This doesn't surprise me. I remember way back attending a seminar on the physiological difference in human eyes regarding the perception of color. This seminar was given by a couple of people from what was then Agfa film. Specifically they were discussing the visual difference back then between Agfa film stocks which were German developed and manufactured and the various Fuji film stocks available at the time that were developed and made in Japan. People were commenting that Agfa color in general had a more "earthy," warmer look and very slight bias towards green versus the slightly more blue/red bias of the Fuji film stocks. We were told that after years of study of the physiological difference in human eyes there was plenty of evidence indicating that Caucasians perceive color slightly differently to Asian due to the fact that there are genetic difference in the cones of our eyes which causes them to react differently to color depending on the wavelengths involved.
"The reason for this is that photoreceptors vary in the wavelengths at which they are most sensitive. For example, one person may have "red" photoreceptors, or "long-wavelength cones", that are most sensitive to wavelengths of light around 564 nanometers. Another person may have long-wavelength cones most sensitive at 568 nanometers. This may seem like it isn't much of a difference. However, this slight shift in photoreceptor peak sensitivity can make all the difference in the world when it comes to perceiving colors as "red" versus "orange", or other colors."
How many of you have heard the comment that ARRI color has a very slight leaning towards green. There are numerous LUTs around that are modified ARRI LUTs that have this very slight green bias dialed out. Bert Degraeve's popular Slog3_Arrilook709_standard vs his Slog3_Arrilook709_balanced LUT that has less green for example. Alister Chapman put out a series of "Venice" LUTs because of requests to have the slight green bias taken out. They were Venice Look -G1, Venice Look -G2 and the standard Venice look which has the green bias typical of the original Venice "look" where it is closer to the ARRI look with its inherent leaning towards green. There have been posts on this forum where the original s709 Venice LUT was considered to be "too green" for some. The generally accepted reason for this green/yellow bias is that most skin tones tend to have a have a higher yellow content than magenta and it's no coincidence that yellow is on the green side on the vector scope. Very subtle negative adjustment to yellow pushes towards green.
"Most Caucasians fall in the range of 5%–20% more yellow than magenta. A fair-skinned Caucasian adult could be as low as 20% magenta, 25% yellow. A bronzed Caucasian could be as high as 45% magenta, 62% yellow."
It has also been hypothesized in certain studies that over the many years of western cultural influence in Asia, starting with Japan specifically since the war that for the Asian eye to perceive color in the same terms as what Caucasians call "correct values" for skin tones Asian eyes need skin tones to have a higher magenta content. In other words a lot of what we perceive as the "correct colors" for skin tones can vary greatly depending on our genetic makeup and then again can vary quite considerably within our own genetic grouping. All this really came to the fore for me when I did eighteen months of a weekly current affairs TV show for TVB in Hong Kong. I was working with two resident Hong Kong producers based here in Sydney and time and time again in post they would request more magenta into interview shots before they were happy. I just had to accept that that is what they saw as normal skin tones whereas for me and my editors at the time we would shake our heads and think "Way to piggy pink" as one of my editors used to phrase it. Maybe just maybe that is why Sony cameras for so long have been accused of a magenta bias. I have no evidence to that but I lean towards thinking that way, just a hunch based on experience.
So this whole talk of what are the "right" skin tones and color science from cameras can only ever be subjective. Two of us sitting side by side in an edit suite can disagree on what we think is a nice skin tone grade just because your "red" photoreceptors, or "long-wavelength cones" are more sensitive to wavelengths of light around 564 nanometers whereas my long-wavelength cones are more sensitive at 568 nanometers. One of us will see more red in the skin tones and the other will see more orange as pointed out before.
I can find no reference to any of the Agfa studies on the physiological differences in human eyes. That seminar was was many moons ago. My short extract quotes come from the following links which may give readers a more in depth look at color perception in general:
http://scienceline.ucsb.edu/getkey.php?key=719
https://help.smugmug.com/correct-skin-tones-for-print-rkUgv14rM
Chris Young
EDIT:
Get your head around this one. A truly deep subject matter.
https://color.psych.upenn.edu/brainard/papers/Brainard_2019_CurrOpp.pdf
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