I only have a puny 50mm f/1.8 but I find when it's wide open it's rather soft (worse than kit lens) and very prone to chromatic abberations so much so that I just usually step it down to f/2.x (somewhere between f/1.8 and f/2.8 but not indicated on lens' aperture dial ring).
But I'd prefer a body with clean ISO 1600-3200 and Image Stabilisation in either lens or body.
you sure not. ive shot weddings at iso1600 with a nikon 50mm 1.8 and the shots came out beautiful! if i were you, i'd get myself an fm2 with a 50 1.4 and iso3200 pushed to 6400 or 12k if you dont mind abit more grain..
thats probably the only way to shoot especially if you are talking about alleyways and sort.
you're talking about a 50/1.8 from 2 different brands. :bsmilie: Unfair comparison.
From cjtune's usage of "IS", I assume he's on Canon?
Anyway, at weddings you might not face CA problems so much due to the lighting conditions.
To answer the TS question... well... naturally the bigger the aperture you have the better... But not forgetting again you may have f/1.2 ... but you might need more DOF... and end up having to stop down anyway. So you have to think about a few other things than just the amount of light your lens is letting in.