13. Two lights that have different wavelengths and intensities may look the same

Question

13. Two lights that have different wavelengths and intensities may look the same (match), A color match between two lights occurs when - for each cone- the response to one light equals the response to the other light. When this happens there is no way that the visual system can tell the two lights apart. Such lights are known as "metamers" (physically different lights that look identical). For example, lights A and B below may be physically different, but you will not be able to tell them apart if the cone responses on each side are the same. Color matching experiments measure how you have to adjust the intensity of one light (e.g. light B) to match the appearance of another light (e.g. light A) cone responses responses to light A to lightB cone a. For the S cones, what would we have to set the intensity (Isoo) of a 500 nm light to, in order to match the response to a 430 nm light with intensity 20? (Use Table 1 to get the S cone sensitivity at 430 nm and 500 nm.) Note we can write the match as an equation response to light A response to light B 20 x the S sensitivity at 430 1500 x the S sensitivity at 500 (S response at 430 nm)(S response at 500 nm,) the required intensity of the 500 nm light (lsoo) order to match the response to a light composed of a mixture of 10 units of 450 nm + 20 units of 600 nm? (Again use Table 1 to get the M cone sensitivities.) cones, what would we have to set the intensity (Isoo) of a 500 nm light to, in 10 x M sensitivity at 450+ 20 x M sensitivity at 600 1s00 x the M sensitivity at 500 (M response at 500 nm) af response to the mixture of 450-600 nm) the required intensity of 500 nm light (ls00)

Explanation / Answer

I500 = 86/5 = 17.2

So I500 required will be ~17.

4500+600 = 500 I500 +1050 = 500

5100 = 500 I500 +550

I500 = 4550/500 = 9.1

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