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Strange focus failures and purple fringe with 760D and 50 f1.8 stm

Started Apr 2, 2017 | Discussions thread
WilbaW
WilbaW Forum Pro • Posts: 11,643
Re: Strange focus failures and purple fringe with 760D and 50 f1.8 stm

macfly66 wrote:

It might look OK but if I crop it...

Did this happen maybe because the middle focus point (which was selected when I took the photo) is covering a much smaller area than on the 350D?

Yeah, nothing is in focus, but the foreground is closest (to being in focus), so I'd say your focus was way short of the car.

Did you focus and recompose, or focus with that framing?

If the second case, it looks like the AF point was over the centre of the bonnet, which is featureless, providing nothing for the system to lock onto. You need to give the AF sensors some detail they can "see" and work with. I would have put the badge under the centre point, locked focus, and recomposed, or used one of the lower AF points if that required less of a recomposition movement.

I know what someone will reply with, so before they do... no! Focus and recompose would not have taken the whole car and foreground out of focus with such a small movement at that subject distance, so that's not the culprit. And if you're worried about that, recompose by moving the camera in the plane of the sensor, rather than pivoting. You'll be amazed how little you need to move to get quite a big recomposition.

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