Still not happy with the D850 AF

Started 2 months ago | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 20,120
Re: Still not happy with the D850 AF

jshen808 wrote:

Put another way - the only reliable way to test AF is with AF aimed at a subject parallel to the sensor.

Right!

Like the below example.

..

Cheers!

I could - and perhaps should have added - with a first class AF subject.

This system is not as bad as a 45 degree ruler - but I am satisfied can still lead to moderately incorrect readings 

The problem is the centre of the target is similar to a geometric pattern when, if the AF point is not perfectly centred, AF can focus a little closer or a little further away than intended.

This is why Nikon caution AF may not be accurate with a geometric pattern.

The Nikon subject for checking D850 AF is a single black/white edge parallel to the short dimension of the frame.

The short dimension of the frame is important as the Nikon D850 (also D500 and D5) uses LiveView focus (which works best with detail parallel to the frame short dimension) as the starting point for checking phase detect AF accuracy.

On the one hand there is no need to buy anything to check focus accuracy with a D850, and on the other hand the Nikon method can only check phase detect accuracy with the central AF point.

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Leonard Shepherd
In lots of ways good photography is much more about how equipment is used rather than anything else.

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