Originally posted by Class A My assumption is that a photographer wants to make a certain image with a certain DOF. That's why Av mode is very popular. If you know what DOF you would like, you simply choose the f-ratio accordingly.
In my experience, this ^^ isn't the case. That is, they are almost never looking for a
precise DOF, they are looking for and are willing to accept
a certain range of DOF, as long as their subject is not compromised.
I think that what matters to most people is, in order: 1) framing (FOV), 2) shutter speed (because motion blur or handshake ruins things beyond repair,) and then 3) noise or DOF. In low-light situations, noise is going to probably be #3 - in well-lit situations, DOF may be.
And here's the thing about #3 - 'too thin DOF' rarely ruins a non-landscape shot or non-macro shot - you have to be shooting close-in portraiture, or some group shots from fairly close-in to have to worry about stopping down because you're not going to get enough of your subject in acceptable focus.
Everyone can think of a case where they had 'too thin DOF' and needed to stop down, but if you look at the % of times that actually happens to you - it's rare. You can accept the DOF range you get more often than not -
much more often than not. This makes the delta between what you get for the same F stop and FOV on aps-c and FF a non-issue, and you can enjoy the noise advantage. It's what SteveM is ultimately describing, and think this is exactly what DXOmark thinks as well, which is why they represent things the way they do.
In other words, if someone's buying a FF camera to shoot low-light, their shooting situations are most often within similar parameters to:
That's the 85 1.8D wide-open - more than enough DOF for what I wanted, and I could take advantage of the F-stop and resulting linear aperture to give me an almost completely noise-free ISO 3600 shot, while maintaining enough shutter speed to stop a moving toddler (1/125s). DOF was 'accepted' (and IMO, is nice.)
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