What happened with the red color here?

[CheshireCat]

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You don't seem to be disagreeing with mjh; as far as I can tell you have just provided the "or" example for his either/or.

The "either" would be the red object R=200, G=0, B=0 and the yellow object R=100, G=100, B=0.

 

This gives "either" red clipped, "or" yellow underexposed.

 

Mjh and I agree on everything but the root cause

I am pointing out that the problem is not the RGB color space, but dynamic range - hence a metering error that will affect both color and monochrome cameras.

 

Let's use your "either" example, and consider 100 as the maximum value of a pixel. Anything above 100 will be overexposed and clipped to 100. Here is what happens with a color camera and a monochrome camera:

 

- Color camera, red object: R=200[overexposed], G=0, B=0

- Color camera, yellow object: R=100, G=100, B=0

 

- Mono camera, red object: Luma=200[overexposed]

- Mono camera, yellow object: Luma=200[overexposed]

 

As you can see, the image is overexposed with both cameras, and the color camera is even preserving details on the yellow object (not overexposed). In that sense, the RGB color space is an advantage rather than a problem

 

If both cameras had 1 stop higher dynamic range, then the maximum value would be 200, and the same exact exposure would be ok in color and monochrome.