Sony A1 A1 focus hunting

[bhphotography]

So I found a very useful function in FastRawViewer, Focus Peaking display mode. I find it super useful to see which of your pictures are the sharpest of the bunch in a sequence (the brighter green, the more contrast, the sharper).

Using that focus peaking view you can really notice how much hunting the A1's AF is doing.

There are some parts of the sequence where the bird has turned and is not really moving, and yet the AF just continuously shifts...

These were all shot on the A1, 1/3000s, f/9.5, 200-600mm 1.4xTC @ 823mm, ISO1000, BirdAF, on a monopod.

Anyone else find that their images are hunt-focusing like this as well?

Maybe it's just bird AF... I'll try using tracking and no tracking next.

 

[Ziggy]

Hmm. I take hunting to mean AF overshooting and coming back several times, and don't see that in your clip.

Focus peaking is revealing what's sharpest.

 

[bhphotography]

Hmm. I take hunting to mean AF overshooting and coming back several times, and don't see that in your clip.

Focus peaking is revealing what's sharpest.

The peaking display is to show you where the plane of focus is shifting. It isn't locked onto the bird's eye plane for some reason--the focus is shifting from the chest and all around. I'm just pointing out that even though the eye is clearly visible, the bird isn't moving (when the shifting is happening), and eye AF is locked on the eye, the *actual* plane of focus still seems to dance around a bit.

I guess the general concensus is that bird AF is not 100% reliable... I only wish I could enable/disable it as part of a registered custom shoot set.

 

[Ziggy]

There's the plane of focus and there's the depth of field - zone of acceptable sharpness.
You're complaining about something the eye doesn't register.

 

[AlphaWorld]

Focus peaking shows the points of greatest contrast, because sharpest focus means greatest contrast (out of focus means blurring, and hence reduced contrast). That’s how it works.

You notice the points along the contrasting edge between what I think are clouds and sky behind the bird?

When there are edges between different colours or shades you will naturally see them show in focus peaking, and when the bird is moving, those edges will move around. It does not necessarily mean that the focus is shifting, only that the high contrast points are moving. Also, these were shot handheld,I suspect, judging by the movement of the timber the bird is perched on - that will exacerbate the apparent shift in focus.

Is this view at 100%, or is it scaled? The scaling algorithms may be further increasing the apparent movement, because most are designed to increase contrast, and work on the pixels contributing to each output pixel - a small movement of the bird or camera changes which pixels contribute to the output, changing the result of the scaling.

This does not look like focus hunting, at least, not like we see in macro shooting sometimes, when the lens goes off on a trip to infinity and back Small shifts in focus, entirely possible (the bird is moving, after all), but it is hard to judge by looking at this focus peaking.

If you want to confirm this hypothesis, try shooting a similar sequence, but with the camera locked down on a tripod, and view it at 100% to eliminate scaling. I’d be interested in the result.