Steffen wrote:I cannot quite follow your explanation, though. Why is shallow DOF a bad thing in low light?
I'm great at these technical explanations aren't I
When it comes to that kind of thing I KNOW you have better knowledge than me so there's every chance I've got this wrong, but here is my thinking. Three things affect DOF:
- aperture size
- focal length of the lens
- distance from the camera to the subject
Shooting at f/2.8 = a wider aperture and (in general) reduces DOF
Being reasonably close to my subject and at 45mm focal length I'm also reducing DOF a little (not as much as if I was using a 200mm zoom from further back though)
Normally I'd shoot at smaller apertures and slower shutter speeds under these conditions and I've always assumed that the only time you'd get away with a wider aperture than that (and a fast shutter speed) would be in very bright daylight.
What Matt pointed out to me is I could have both a small aperture and a faster shutter speed if I had enough light (the flash). This in turn would give me a nice sharp subject (the less the shutter is open the more stable the camera), but that I'd also reap the benefits of the shallow DOF in making for a more blurry background. The best of both worlds. This is where I know I got it wrong - I said greater DOF on Matt, but in fact it's greater sharpness. a very different thing. I hadn't realised that until I pondered your question.
Steffen wrote:And how would the use of flash alter the DOF (once the shooting distance, focal length and aperture has been chosen)?
It can't - once all three are set, DOF is cast in stone. mea culpa - it really allows for a faster shutter speed and so a sharper image at the SAME depth of field.
Does that make sense. Or have I got something else wrong?
And if I have got it wrong I have no problems being told so since I know I have lots to learn.