GH5 Question about Contrast-Detect AutoFocus

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Ianscreations

Well-known member
Since the GH5 uses Contrast-Detect Autofocus, would it make sense that shooting in a shallow depth of field would help the camera target better?

Back when the autofocus debate raged forward, I was doing my own test with my (very patient) son.

https://vimeo.com/213089607/2559480acb


I deliberately shot against a background with a lot of contrast and used the most shallow depth of field to really push the limits of the autofocus abilities.

But in the real world, I usually shoot wedding processionals with a deeper depth of field to give myself more range to keep the subject within focus.

But I started wondering...would it actually help the camera to focus if I used a more shallow DOF? Not sure where the "contrast detection" actually works. To me, there is greater contrast between a subject with a shallow depth of field than a subject in a deep depth of field.

Thoughts on that?
 
Well, this is either a dumb question or no one knows the answer to it. Or no one gives a flip. Either way, I'm throwing out the line one more time ;)
 
Well, I would assume contrast detection autofocus would depend largely on the contrast of image tones on the subject. If working in an environment where backgrounds have a lot of contrast that might compete with the subject, I would narrow the focus area so it did not really include background detail. Shallow depth of field should be used when appropriate to the subject and the same for a deep zone of acceptable sharpness. Not for autofocus performance.
 
OP, I think this is an interesting question. Unfortunately, I have no idea. I would try to test it with my Gx85, but currently I have no fast autofocus lenses. And we'd need to decide on a test that would prove or disprove the theory.

I would think your premise is correct. Technically, it would get more information to depth of defocus with a fast lens. So it would be able to focus "better". BUT, it also needs to be that much more precise! So the two things - the demands of a narrow depth of field, vs. the information the camera has to target focusing, should cancel each other out to some extent.

I played with GH5 in B&H this week. My first time using the camera. It had the 12-60 kit lens. I will say that pull focusing of static subjects was much better than I feared. Sometimes it missed, but in general it was pretty darn good. This was just to focus on one stationary subject, then adjust framing or touch the screen to focus on a more distant or closer stationary subject.
 
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