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Old Feb 25, 2013, 12:38 AM   #1
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Default Why do the green and luminance histograms match?

I know the green (G) histogram closely resembles the overall brightness (luminance L) histogram. Is it because green is in the middle of the frequency spectrum (VIBGYOR) and is representative of the average/overall light?

If so, on a picture with mainly blue & red subjects (i.e only high and low frequencies, and no green subjects), will the G histogram be zero (nearly) making it completely different from the brightness L histogram?

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Old Feb 25, 2013, 6:03 AM   #2
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Yes, green is in the center of the visible light spectrum. Also, in a Bayer Filter, there are twice as many photoreceptors for green light as for red and blue light. As a result, the green histogram and the luminance histogram are very similar under most circumstances. But, yes, when the frame contains lots of bright reds and/or blues, the differences will be greater
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