D7100 substantially better AF than D7000??

Started Apr 14, 2013 | Discussions thread
bluescript New Member • Posts: 1
Re: D7100 substantially better AF than D7000??

Gene Goodman wrote:

…. My main problem is AF consistency. I find that focus is spot on, then not. I fine tune and come up with one value, then then a week later its a different value, example from 0 to -6, or -8 to -14….

Hi,

Saw the main thing when testing a brand new D7000 against http://www.peleng8.com/pic/FocusTestChart300dpi.png target using 75-300 VR some months ago, shooting supported camera at 300mm, no VR, mirror lock, etc, using the central AF point only.

1) using micro adjustment, the camera could be tuned to be accurate ON AVERAGE, with significant spread still present to both back and front focusing.

2) the micro adjustments required to fix the average varied from day to day

Surprisingly enough, D5000 using only central AF point in the same test performed better in the sense that both the average was  effectively on target day on-day off and the dispersion of individual readings around the mean was smaller than on D7000.

My wild guess is that the AF sensor on D5000 is larger than on D7000 and hence 'more accurate' since the object distance is deduced from triangulation of signals from two closely placed detector points on the sensor. The smaller the AF phase detector on the sensor is, the the closer the two points need to be and hence the accuracy drops because it will be more difficult to to read the subtle differences in triangulation

Regards

Armin

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