On Mar 21, 2:47 pm, Bob Williams wrote:
Pooua wrote:
http://web.mit.edu/neltnerb/www/artw...x.htmlfeatures artwork
illuminated by super-bright LEDs, but the photos do not accurately
reflect the colors of the lighting. The artist says that his camera
has trouble picking up the purple lighting, instead showing it washed
out, apparently because it is outside the normal color space of the
imaging sensor. Does that sound likely? What might a photographer do
to take better photos of these tricky lighting situations?
I think the reason is, that NO combination of RGB used in sensors can
produce violet (purple?) light. The visible color spectrum is ROYGBV.
All colors between R and B can be generated by mixing appropriate
amounts of R, G, and B. But Violet is a shorter wavelength than any of
the frequencies captured by an RGB sensor. So no combination of longer
wave lengths can produce a shorter wavelength.
You can't fix it with Photoshop either because PS also uses an RGB
palette (e.g. Adobe RGB).
Bob Williams
I don't know if that explains the problem.
1) Purple is actually a combination of red and blue.
2) The cones of our eyes only detect red, green and blue (some
extremely rare women can see a 4th color)
I just found a website that states that humans detect violet by
comparing the ratio of blue light to red light. According to the
article, humans could just as well use the ratio of blue light to
green light, but the human spectral response to green and red light in
the blue portion of the spectrum is about the same, so it does not
make a difference which system humans use.
Digital cameras, OTOH, are more likely to sense violet by the ratio of
blue to green light. So, the response is not the same. That's my take
on what the article is saying, anyway.
http://gene.bio.jhu.edu/violet/violet.html
It would seem from this that it would be possible to switch the green
and red channel to find the violet. Maybe. Possibly. But, what happens
to everything else in the photo?
Anyway, I am thinking that by beating the scene into submission
through the clever use of RAW mode, bracketing and maybe HDR, I ought
to be able to help this artist. Too bad that he is in Boston, while I
am in Dallas.