Help me calibrating my old 50D f1.4 on the D800

Started 3 months ago | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 15,543
Re: Now AF point sensitivity coverage

fishy wishy wrote:

There was a very experienced sports shooter that tried to tell me that the focus sensors extended beyond the bounds of the focus boxes. I tested the model of camera and could not see what he was talking about.

It is a bit tricky with a D5/D850 or D500 to check that the sports photographer is 100% right as in single point AF there seem to be some surrounding none user selectable AF points operating.

With any previous camera body start by doing what the sports photographer did by selecting a contrast colour line (maybe from a marker pen) ideally black on white as AF sensors detect contrast rather than individual colours.

1/ in single point AF aim the AF point on a featureless part of the subject,

2/ press and hold the shutter button and wait a second or two, for AF to stop hunting,

3/ slowly move the AF point toward the contrast line, keeping your finger on the shutter button

4/ observe AF activate a little before the AF viewfinder point edge reach the line.

This confirms AF does detect detail outside the boundary of an AF point.

5/ AF activates further away from the target line in AF-C than AF-S.

The "wider" sensitivity is likely to assist AF acquisition being passed from one AF point to another when multi AF points are being used during AF-C.

It can help reduce occasional camera focus on an unexpected subject if you learn where AF can detect detail which is not within an AF rectangle.

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

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