Howiethek wrote in post #15226141
I haven't read the entire thread but I did shoot with lens cap on to try and determine at what ISO, I would see unacceptable (for me) noise. Does this minimal light leaking in, affect conduct of performing an ISO noise assessment?
I'm not sure how that test would help you judge noise in the real world. Noise is affected very much by underexposure, shoot an image correctly exposed at 6400 ISO and you will see less noise in the shadows than if you shoot using 1600 ISO but two stops underexposed. In that instance 1600 could give you unacceptable noise whilst 6400 is still acceptable.
Shooting with the lens cap on is using so little light (essentially what can get in through the viewfinder) that you are almost certainly producing a severely underexposed result which will create noise that you wouldn't normally see in a normal, correctly exposed, image at that ISO.
If you want to test to see at what ISO unacceptable noise becomes an issue, shoot real images, exposed correctly, and judge from those. Inventing tests that bear no relationship to real world use will give results that ALSO bear no relationship to real world use. That is why there was such a fuss by those who tested their cameras with the lens cap on, and discovered the light leak "issue". In real world use, the issue doesn't exist (unless you shoot with the lens cap on all the time).