by dubaiphil » Thu Oct 30, 2014 3:35 pm
It all depends on what your ISO threshold is for your camera - what you're willing to push to and still have acceptable results in your opinion/for your needs.
And if what you're shooting is relatively static or moving, and how close you're going to be. (e.g. shooting people walking relatively close with a 50mm will still need a relatively fast shutter speed of around 1/200th, whereas if it's a scene with people standing you could push that shutter speed down to around 1/50th)
IMO at night in a market an f2.8 won't be enough, unless you've got a bang up to date body that performs well/acceptably at 12,800 or 25,600ISO
Different focal lengths will change things too - 50mm and you'll be less wide, meaning that your subject may be better lit if you're matrix metering, requiring a lower ISO. For example, a lit stall at 50mm may will the fram, whereas at 30mm and the same distance to the stall you'll have street, background and dark sky in the frame too - in matrix your camera will push the ISO up to compensate if you're on auto ISO
