Lens speed more important than I thought for subject detection performance

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C

Calson

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I have been using a Z9 with the 100-400mm f/5.6 lens to photograph birds at my hummingbird feeders. The usual camera to subject distance was 15 feet. The Z9 was having difficulty in bird mode focusing on the birds heads and eyes. I switched to the 70-200mm f/2.8 lens and the focusing problem was resolved. Even with the 1.4x teleconverter attached which gave me a 98-280mm f/4 lens the performance was considerably better than with the 100-400mm lens.

I would not have thought that the difference of one f-stop would make that amount of difference with the autofocus performance of the Z9 camera. In particular with subject detection the additional light is clearly needed for optimum performance.
 
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It shouldn't, because the z9 is capable of good af all the way past f9 (ask me how I know).

There are many factors, but the lens doesn't impact how quickly the af finds a subject, or not. If it does, then there's something else going on, because the af is internal to the camera. One stop is nothing.
 
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Steve recently put out a video that showed that in some circumstances using a differnet focus mode to what seems obvious can give better results. With these modern subject recognition modes changing the focus mode is/should be one of the things we do routinely if esults are not good.
 
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