High ISO performance is nothing without low light autofocus performance

Started Dec 19, 2012 | Discussions thread
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primeshooter Veteran Member • Posts: 4,260
High ISO performance is nothing without low light autofocus performance

I guess this is obvious, but I have really been noticing this lately. In pretty poor light where you have to up your ISO speeds to over 3200 for a half decent shutter for your focal length and with this in mind being at f/1.4 (so pretty low light situations) I find the D800 has considerable trouble locking onto the sometimes low contrast eyeball / eyelashes of a subject. Nikon, and everyone else claim the AF performance of the D800 is better, but my hit rate is definitely noticeably lower. I know low light is the most challenging thing for AF modules and I am using the centre point but still I am underwhelmed!

NB: Let me disclaim this right here - it's not about subject motion or blur, it's about the lens / D800 body focusing in front or behind of the intended point - extremely frustrating. In good light, the AF locks on to where I need thus AF fine tune is useless. What I also find is with many lens combinations they are quite accurate in close distance but moderate to far they are worse (which seems a paradox as dof is obviously much greater further away so you would think this would be the other way around).

I am going to run some more really low light tests. What is the point in having an f/1.4 prime and an amazingly good high ISO performer like the D800 if it can't seem to focus where you want it too? Yes, I know how to use flash but sometimes I am shooting in available light for a particular reason, and so far I am pretty frustrated with it. This could just be that now there are 36 million pixels, AF being slightly out looks really bad at 100% wheras it wasn't noticable on the D700 i.e. AF accuracy was always poor with nikon and now we are only really seeing it.

I am sure many will chime in saying it is amazing but seriously, try it with the 24mm 1.4G, the 50mm 1.4G the 85mm 1.4D and G in poor light, and try and get the eyeball you want in perfect focus (they seem terrible atm to me) Obviously your shutter will need to take into account your focal length and may well need x2 the speed etc. ISO perfomance - great. AF accuracy poor. The two need to be connected.

I will take any logical advice also!

Leica X2 Nikon D700 Nikon D800
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