View single post by Robert
 Posted: Fri Feb 2nd, 2018 16:44
Robert



Joined: Sun Apr 1st, 2012
Location: South Lakeland, UK
Posts: 4066
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Can't speak for the D850 specifically but I think this applies.

The focus points are exactly the same between the D5 (FX) and the D500 (DX) meaning with the FX sensor the focus points are clustered in the centre with the periphery bare of focus points. With the DX, the focus points cover almost the entire screen.

This means, effectively, a target bird is more likely to be picked up anywhere in the viewfinder of a DX camera, whereas with FX you HAVE to keep the target bird in the centre of the viewfinder to stand any chance of locking on. Once locked on, the camera will track the target bird almost magically anywhere within the AF point area. But with FX, the AF point area is effectively quite a bit smaller.

Edit: To improve clarity.



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Robert.