From what source is the picture taken? How are the curves achieved, are they drawn by hand or are they actual results of some reasearch project?
Color sensitivity curves indicate we cannot perceive violet
I have seen on a discussion here [1] that it is important to indicate that the L cone has a secondry but small absorption peak at short wavelengths otherwise we wouldn't be able to perceive violet (which we perceive when we look at 400nm or if we look at red and blue light together). This seems to be missing from the cone sensitivity image, maybe this is becuase the red curve stops about at this point Any ideas? 89.168.123.190 (talk) 14:22, 17 May 2009 (UTC)[reply]
No, as far as I know there is no second peak in the violet. On the right is an image I made using data from here which shows no second peak (although there is a slight downward concavity, so maybe in different units you could "get" a peak). At any rate there doesn't need to be a second peak, there only needs to be a change in the ratios of the SML cone responses, and there is because M and L still respond noticeably at low wavelengths. The description of color vision on the page you linked isn't accurate. Color monitors can reproduce all hues, including violet, but can't reproduce highly saturated colors. For what it's worth here is a spectrum of the RGB phosphors of one CRT, showing that the B phosphor shines all the way into the violet. -- BenRG (talk) 15:50, 17 May 2009 (UTC)[reply]
I agree. No secondary bump is known. You do see it in RGB color matching functions, indicating that you need to add some of red phosphor's light to get to violet's hue angle. As Ben says, though, you can't make a saturated violet from blue and red, just a purple approximation at the same hue angle. In the color matching functions, that's because the green curve is negative at the 400-460 nm wavelengths, meaning you're outside the color triangle. Dicklyon (talk) 16:10, 17 May 2009 (UTC)[reply]
It's not really a peak, but I think "bump" is a good word. See File:Cone-response.svg for a better view. —Soap— 00:38, 14 July 2011 (UTC)[reply]
hi guys. if the secondary peak is not there, why you would confuse purples and violets? anyway it seems to me that the secondary "bump" was measured so far:
http://www.babelcolor.com/download/A%20review%20of%20RGB%20color%20spaces.pdf — Preceding unsigned comment added by 151.18.76.131 (talk) 17:38, 9 October 2015 (UTC)
http://psy2.ucsd.edu/~dmacleod/publications/61StockmanMacLeodJohnson1993.pdf
http://www.researchgate.net/profile/Timothy_Kraft/publication/19353982_Spectral_sensitivity_of_human_cone_photoreceptors/links/00b7d52af61cdd7e11000000.pdf
http://www.sciencedirect.com/science/article/pii/S0042698900000213[reply]
and a rapid search gives many responses like these:
http://www.color-blindness.com/2010/03/09/types-of-color-blindness/
http://webvision.med.utah.edu/book/part-vii-color-vision/color-vision/
http://biology.stackexchange.com/questions/1446/why-can-cones-detect-color-but-rods-cant
https://www.unm.edu/~toolson/human_cone_response.htm — Preceding unsigned comment added by 151.18.76.131 (talk) 17:29, 9 October 2015 (UTC)[reply]
