Aperture/ISO Hypothetical question
Heres a hypothetical situation for you all
I have an f2.8 lens which is very decent wide open but razor sharp at f4
Depends on the lens.
My D300 gives me acceptable noise at ISO 400 but gets a bit noisy by ISO 800
Depends on the light.
For the purposes of this situation lets also say that DOF is irrelevant to the final picture...
I presume then that your subject is a flat target shot at a 90° angle.
To get an acceptable shutter speed, i can either use f2.8 @ ISO 400 or f4 @ ISO 800.
No flash, I presume.
From a purely abstract point of view, you are asking about a trade-off between sharpness and noise which vary based on the lens and the conditions, and have to be evaluated subjectively.
, if you can selectively sharpen the subject with the less sharp aperture, you may get it reasonably close to the sharper aperture while keeping background and shadow noise tamed.