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I can find several qualitatively different diagrams of the responsiveness of human cones and rods to different wavelengths of light.

A page referencing Bowmaker and Dartnall, 1980 has the following diagram (which indeed matches that from their paper):

                   enter image description here

Very similar plots (with the same truncation for M and L cones, and the same slight rise in sensitivity at shorter wavelengths) can be found here.

For a graph with an even sharper nonmonotonicity of the L cone at blue wavelengths, see here.

On the other hand, some diagrams show much more mountain-shaped response curves, like those derived from Stockman & Sharpe at this page (which produce for instance Wikipedia's graph):

                    enter image description here

Similar qualitative graphs can be seen in this figure, this one, or this one.

My vague impression is that the second category of graphs tends to come from more recent or reputable sources, but I'm very unsure about this, and in general I'm confused why there seems to be so much disagreement here. Are there good survey articles that discuss this discrepancy and the reasons for it?

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    $\begingroup$ The first one seems to indicate strong response into the ultraviolet - the discrepancy could be that the first is in-vitro, the second is with the lens in-place which blocks the ultraviolet. Can you clarify the conditions of measurement? $\endgroup$ Jan 9 at 23:04
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    $\begingroup$ @ARogueAnt. It sounds like Bowmaker and Dartnall removed the lens: "The eye was dissected under dim red light (Kodak safelight no. 2). An equatorial section of the globe was made, and the anterior half lifted away. The vitreous body was then removed from the posterior half without disturbing the retina, and the remaining eye cup placed in ice-cold mammalian Ringer solution of pH 7 1." And I believe Stockman & Sharpe used live subjects, so that would seem to explain it. $\endgroup$ Jan 9 at 23:15
  • $\begingroup$ That fits at least with the UV response. I'm not sure about the scaling though, I'll bow out. $\endgroup$ Jan 9 at 23:18
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    $\begingroup$ It sounds like a issue with the precision of the graph. high precision graphs are not smooth curves $\endgroup$
    – John
    Jan 10 at 1:10
  • $\begingroup$ Welcome to Biology.SE. In the absence of units, some sort of internal standard, or any other way of meaningfully comparing these curves I would say it is impossible to make valid comparisons. Do any of these publications claim there are disagreements? If so, can you please provide a quotation and reference — if not, I think the "discrepancy" is probably illusory. $\endgroup$
    – tyersome
    Jan 10 at 20:10

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