Still not happy with the D850 AF

Started 2 months ago | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 20,098
Re: Still not happy with the D850 AF

Nils wrote:

https://www.opticallimits.com/nikon_ff/998-nikkorafs10514ff?start=1

It can be clearly seen the point of focus wide open is (100) ....... even given the increasing DOF when stopping down focus cannot hold the "100" in focus .........

........ quite a slip up from Nikon.

Great link. Appreciate it. Thanks!

You are spot on with your POV btw!

Or perhaps not 

If starting AF from infinity, AF can lock on the first area with sufficient contrast for the AF to detect within the depth of field.

As dof increases as the lens is stopped, when using a 45 degree ruler with AF started further away than the 100 mark there can be (and sometimes is) enough contrast within the dof for AF to lock on before it gets as close as the intendeds 100 mark on the ruler.

If starting from minimum focus, as the lens is stopped down there can be enough contrast for AF to lock on in front of the 100 mark.

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

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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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