The concept of "equivalence" in renderer lighting does come up occasionally and I see people arguing that you should do color chip variation and keep intensity 100.

But let's examine this notion. (Sticking with gray scale color chips for the sake of simplicity.)

The effective strength of a light is the color multiplied with the intensity:

C * I

Where C means the color chip value and I means the intensity.

However, since color chips are affected by gamma, that's not the whole truth. The whole truth is:

(C ** g) * I

Given a light with a color chip set to RGB 186, 186, 186 and intensity 80%, what is the effective strength?

((186 / 255) ** 2.2) * .8 = 40%

Did you expect the light to be so dark when using a light gray? Probably not.

The key point: color values are nonlinear. Making a modest decrease in chip color will produce a dramatic decrease in brightness. This is intentional. It let's us represent a wide range of colors using only 8 bits. That's why sRGB is set up that way. We need lots of dynamic range. Linear values would not give us enough range to work with. The non-linear nature of digital color values is helpful in achieving realistic looking images with fewer artifacts - linear values would look banded as you got down to the lower values.

Second key point - humans are not good at thinking nonlinear.

So - you're asking for trouble if you mess with a nonlinear control system using your linear intuition.

For my case above, an equivalent setting is WHITE color chip (C = 1) and I = .4.

((255 / 255) ** 2.2) * .4 = .4

Now if I want to increase intensity by just 10%, I can type in 44%.

If you can figure out how to get 44% using gray, then by all means you can use the equivalence of factors in multiplication, but you have to take into account that the C value is nonlinear. If you can do that, use C when you feel like it. If you can't, use I instead.

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