Why bother changing base ISO?

Started Jul 18, 2007 | Discussions thread
kevm14 Senior Member • Posts: 2,253
Re: There's no red data in the sky

Tom Christiansen wrote:

Even a "clear blue California sky" is going to have a red-channel
multiplier. And just how much red signal can there be in a blue
sky anyway? It's the same problem as blue channel in incandescent
light. You have very little signal to start with, boost it 3 stops to go
from ISO 100 to pseudo-ISO 800 equivalent, then further add
distortion by a white-balance coefficient. GIGO, magnified.

But that was a daylight shot, so working from a daylight WB perspective, the red channel wouldn't have had to be pushed to obtain the correct WB. I don't see why the sky should be noisier in the ISO100 shot pushed 3 stops vs the 800 shot.

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