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Alan Wallace

Manual Focus Jerky Motion - 10/24mm Lens

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My new XF 10/24mm lens when fitted to my XT3 has an intermittent problem. When in portrait mode (and only portrait when the hand grip is uppermost, not grip downmost) the focus is jerky in manual. If I turn the focus ring clockwise the focus distance indicator will not move, then move towards the infinity end of the bar, then maybe stutter and jump backwards a bit, then jerk towards the infinity end again. Ultimately it gets there but it staggers like a drunk. The happens whether focusing in or out, and is not consistent, it is quite random. In auto focus it's fine. In landscape orientation and portrait grip downmost it's fine. The issue starts about half way between landscape and portrait (grip uppermost).

I have tried with OIS on and off, no difference. I have two other lenses and both are fine.

So the lens went back to Fuji under warranty. They stripped the lens, adjusted it,and said all is good. 

When I received the repaired lens it had the same problem. So I borrowed a different 10-24 from the camera shop and that lens worked fine. So, I thought the problem was definitely my lens. But I then tried by lens on an XT4 (no XT3 available in the shop) and it worked fine on the XT4. So I am now thinking maybe it's a combo problem of my XT3 and my lens. I checked and the firmware is up to date in both camera and lens.

In a final attempt to fix the problem the camera shop reset my camera. At first I thought this had fixed the problem, but it hasn't. 

Before I send my camera/lens combo to Fuji I thought I'd check if anyone else had come across this problem. Thanks.

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Hi Alan - I was trying to recreate the problem you're seeing with that combo. The one thing I can say is that it takes a LOT less of a turn of the focus ring to get from 5' to infinity than to get from minimum focus distance to 5'.

Couple of quick questions - do you know if your camera's focus ring operation is set to linear or non-linear? Not sure how significant of a difference that will make. But the other thing I noticed I that when your aperture is wide open on that lens (ƒ4.0) you can push the focus past what appears to be infinity. When that happens a large twist of the focus ring will make it look like it's jumping suddenly. Just to see what I'm talking about, set your lens to ƒ22 and then move towards infinity as slowly as you can. You'll notice that the depth of field indicator (blue line) will continue to move towards infinity even after your effective focus appears to be at infinity.

Kind of hard to explain, but hopefully that makes some sense

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Hi,

Thanks for taking the time to 'have a play' and see what happens. Firstly, I'll reply to your comments/suggestions.

Yes, I too note that you need a LOT LOT more movement of the focus ring when focusing close up. This is great as I can fine tune my focus when focusing close up as I need precise focus due to the shallow DoF when close up.

I have played with linear and non-linear and it doesn't make any difference as far as I can see.

I understand what you mean by the DoF indicator still heading to the right when the focus line (whiteline) is at infinity. Mine does that. It also does it at f4 but it's harder to see as the DoF indicator is so small then. But the problem I experienced wasn't there.

I could be focused at say 1m and slowly move to 3m but in that process as I am turning the focus ring in one direction smoothly the focus line and DoF indicator would say start to move right, then stutter and go left and then back to the right. Sometimes the jumping was very dramatic. But this happened only when in portrait mode with the grip upmost.

However, today I put the lens back on to mimic your testing and lo and behold the movement was as smooth as silk in linear and non-linear, and in portrait and landscape. So I have no idea what's happening. It looks like someone has swapped lenses on me!!! It's all under warranty so I'll keep an eye on it. What had me puzzled was that when it was 'playing up' it seemed to be a 'my camera-my lens' combo problem. The lens was fine on another camera and the camera was fine on another lens.

If it starts playing up again and Fuji fix it out of courtesy I'll let you know what happened.

Thanks again, Alan

 

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Huh, that is super strange. But hopefully it works smoothly moving forward. The only other possibility I can think of is that maybe your thumb had triggered a focus lock or auto-focus because of how you hold/support the camera in a portrait vs. landscape. But that doesn't necessarily explain why it happens on the x-t3 and not another camera. 

I'll just keep my fingers crossed for you :) 

 

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