GF 35-70 AF-S at MFD

Started 5 months ago | Discussions thread
Tokitaro Forum Member • Posts: 87
Re: GF 35-70 front focusing issue documented

JimKasson wrote:

MF ratios wrote:

JimKasson wrote:

Zorki-6 wrote:

JimKasson wrote:

Zorki-6 wrote:

Thanks to Jim for confirming that the issue seems related to a faulty batch, as I'll now be back on to Fujifilm for yet another replacement.

Here's a video and a couple frames demonstrating the problem that I and a few others are experiencing (hopefully this will help people identify if their lens is a bad copy):

https://drive.google.com/file/d/1kvMPAUcpuZprTjQHi0d88OQ32Dy4bNb4/view?usp=sharing

AF - c. 3-4cm front focus close to MFD at 70mm

AF + MF (manually focused to account for front focus)

This isn't rigorous but it'll do, as it shows that the problem occurs consistently and that it isn't user error. I don't have a single correctly focused frame from this lens or the copy I had before it when using AF close to the MFD. The problem presents the same on the 50S II, 100S and 50R. If you do find that your 35-70 is front focusing, it might be useful to share your region and whether you bought it as part of the 50S II kit.

First copy of 35-70 - seemingly identical amount of front focus

When I do ramp AF testing, I have a portion of the target orthogonal to the lens axis, and that's where I focus. If you ask a camera to AF on a ramp, the results are usually not what you'd get if you use manual focusing.

It's harder to get the ramp/orthogonal setup aligned as you get closer, so I don't use it at distances akin to the 35-70 MFD.

I've no doubt the methodology is imperfect but the result consistently replicates what I'm seeing out in the wild, 3-4cm front focus using those parameters. The 80mm and 120mm are also able to AF perfectly on that target.

I'm very familiar with this issue because I spent a couple weeks working on a project that required the decent close focusing offered by the 35-70. I had to resort to AF + MF to compensate for the front focus every single shot, but my main frustration was that the front focus was more consistent than the MF behaviour. In the end I dropped £2500 on the 120 and didn't look back.

I'm confident that a good copy of the 35-70 will be a very capable lens, notwithstanding some flare and halos wide open. Your testing should hopefully confirm that.

I can certainly confirm the flare wide open and up close.

I got a 35-70mm from the kit batch and have the same issue. The firmware version is 1.00. Any chance that Jim has one with a version 1.10 or higher? That would give some hope for a futur release to fix this.

My 35-70 is FW 1.0.

Thanks. Back to Fujifilm yet again. There are no parts for the 35-70 in Poland and maybe the whole of Europe so I'm not sure how they'll handle this.

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