Why don’t camera sensor RGB filters match human cone spectral responses more closely?
Asked 1/5/2021
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It’s often said that RGB camera sensors are designed to match human vision, but published spectral-response curves for Bayer filters look quite different from the eye’s cone responses. Human cone sensitivities overlap heavily, while typical sensor red, green, and blue filter curves are shifted and shaped differently. Why is this mismatch so large, and how do cameras still produce accurate-looking color? Does this mean cameras need significant color crosstalk correction in processing?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
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This is a remarkably complex and interesting subject and no answer will be comprehensive.
The TL;DR result is that if the final picture looks acceptably like what you perceive, then it works.
Your eye spectra diagram seems a little compressed. You don't say where it came from. Here's one from Eye and Colors: 
The color filters used for sensors will never match human spectra sensitivity. Not even humans match other humans. The question becomes whether or not you can manufacture and produce color filters that can be acceptably processed to produce a result that works. On top of the mismatch in spectra of the filters mentioned, sensors also use twice as many green sensors as a way to bump up green sensitivity to more closely match typical human color perception.
Could the color filters more closely match human spectra? Probably, but at what cost and benefit when a little software already handles the corrections?
On top of camera processing you also have the question of presentation.
Various display devices have their own spectra that also don't match the human eye. For example, the Samsung Quantum Dot vs Conventional TV:

This too requires its own processing to produce results that are desired or acceptable.
For even more esoterica, you may want to delve into All the Colors We Cannot See, and Red-Green & Blue-Yellow: The Stunning Colors You Can't See
Originally by user77199. Source · Licensed CC BY-SA 4.0
user77199
5y ago
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Camera RGB filters are not meant to be a literal copy of human cone responses. The practical goal is simpler: capture enough separable color information that processing can turn it into a pleasing, accurate-looking image.
Human vision itself is not a fixed set of clean RGB channels. Our cones overlap strongly, people differ from one another, and the eye/brain performs substantial interpretation and adaptation for different light sources. So “matching the eye” is only approximate to begin with.
Camera filter design is a compromise between manufacturability, sensitivity, noise, and color separability. Bayer sensors also use twice as many green-filtered pixels, partly because that better supports luminance detail and aligns more closely with perceived brightness.
Yes, cameras rely heavily on processing to map the sensor’s raw responses into standard color spaces and to reduce channel crosstalk. But that is normal, just as human vision relies on brain processing. What matters is not whether the raw spectral curves look like cone curves, but whether the system as a whole can be calibrated to render colors acceptably under real-world lighting.
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