35 GM AF ISSUES

Started 2 months ago | Discussions
jonpais
jonpais Veteran Member • Posts: 3,039
35 GM AF ISSUES
1

After purchasing the Sony 35mm GM yesterday afternoon, the very first thing I did was to run the serial number by Sony to see if mine was one of those with the defective ornament plate, which fortunately it was not. But it appears to have a far more serious issue; while recording myself wearing glasses next to the window – as I’ve done previously with the 20mm f/1.8 G, the 35mm f/1.8, the 55mm Sonnar, the Sigma 85mm DG DN and even the 135mm f/1.8 GM – the AF keeps hunting, seeming to lock on, then readjusting itself yet again, never focusing on my eyes.

(skip ahead to 3:55)

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Jeff2013
Jeff2013 Veteran Member • Posts: 3,098
Re: 35 GM AF ISSUES
1

Sorry to hear about your problem.  I have watched and read just about every review on this lens and Eye Focus has seemed to work really well for others, so I assume that your lens has corrupted firmware or other malady.

I'm still waiting on mine, but this will now be the first thing I test when I receive it - even before 'centering'.  

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f1point4andbethere
f1point4andbethere Regular Member • Posts: 370
Re: 35 GM AF ISSUES

Weird. What camera was this shot using?

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Sony a1
pollup Contributing Member • Posts: 940
Re: 35 GM AF ISSUES
2

f1point4andbethere wrote:

Weird. What camera was this shot using?

a7s III

There might be compatibility issues between the a7s III and the 35GM, it's the kind of things we've seen in the past. Or it might be a defective unit.

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Beatsy
Beatsy Senior Member • Posts: 1,016
Re: 35 GM AF ISSUES (with A7rii too?)
1

Hmmm, funny you should mention that. I put the 35GM on my A7rii this afternoon and had real problems with tracking. Even in good light - bright sun or bright/cloudy.

It would lock the object under the focus spot on a half shutter press but instantly skitter off to some random spot and expand a box there that often reached half the size of the scene (with heaven-knows-what in focus). The non-tracking AF modes were all good.

I thought I'd misremembered how good (bad) A7rii AF tracking was. It's been bolted into a studio macro rig for over a year while I used A7riv and A9 for AF togging. It's very easy to get used to the newer versions and assume everything works like that. So I didn't look any further into the issue - until I read your post.

I just tried a Zony 35/2.8 on the A7rii instead. It locked and tracked *much* better than it did with the 35GM earlier. So I checked the 35GM again, same settings, and guess what? It worked *much* better than this afternoon too!?! Sheesh!

So not much help as I couldn't reproduce the issue, sorry, but there could be a V1.0 bug (in the lens) affecting compatibility - it has happened before.

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jonpais
OP jonpais Veteran Member • Posts: 3,039
Follow-Up
2

This afternoon, I compared the 55mm Sonnar, the 20mm f/1.8 G and the 35mm GM, all under the same lighting conditions and with identical settings. Aside from perhaps one instance, I was unable to replicate the hunting behavior I'm seeing with the 35mm with any of my other lenses. During my tests yesterday, the 35mm exhibited hunting no fewer than a half dozen times, and there is at least one instance of it in today's video, though less severe. I don't recall having seen this with any of my other lenses.

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andrewD2
andrewD2 Veteran Member • Posts: 9,445
Re: Follow-Up
2

My guess is that it is due to the high amount of focus breathing.

Andrew

jonpais
OP jonpais Veteran Member • Posts: 3,039
My Bad!
2

I'm happy to report that the fault was all my own. After changing transition/sensitivity settings from 4/3 to 3/3 and recording for around three to four minutes in the same harsh lighting conditions, rocking back and forth from very close to a few feet away from the camera, while wearing glasses, the lens did not falter at all. Also, the lens is blisteringly sharp! Now, really looking forward to the 50 1.2 and 14 1.8.

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