I'm still learning the basics and trying to fully understand the balance between ISO, Aperture and shutter speed.
My question is here, in Low light situation, people tend to refer to on stop in aperture as say F5.6 to F4, or F4 to F2.8 etc. Could someone tell me does this stop has the same effect dumping up the ISO to from say 400 to 800, or 800 to 1600 etc?
I'm trying to understand if you don't have pro grade glass and went for cheaper alternatives which are considered soft wide open. In low light situations would you assume you get the same grade quality with the below. All else being equal, ie camera & shutter speed etc
F2.8 at 400 ISO (lets say sigma)
f4 at 800 ISO (lets say Nikon's pro grade)