Truly equivalent ISO values for FF and m43 are different by the factor of 4, the FF ISO being four time greater than the m43 ISO, e.g. FF ISO 1600 is equivalent to m43 ISO 400, when the lenses are equivalent.
Didn't mention "equivalent" ISO, just the value; FF ISO-400 vs m43 ISO-400, not FF ISO-1600 vs m43 ISO-400.
When I change SS, I check the ISO first before I double check the SS to make sure the SS is acceptable. IBIS and OIS come into play on how much SS I can get away with. Yes, I understand what you were saying, but in practice, with so many variables, it might or might not apply: I am comfortable with OM-1 1/40s @ 420mm, but with the G9II, I get less keepers @ 1/200s (2+ stops in ISO), due to the IS. Same sensor size and same lens. I pay attention to equivalent FL and aperture (DoF), but I change SS constantly, I care about the absolute ISO, and the equivalent ISO, not so much.
Nov 01, 2025 at 11:58 PM
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