Schneider 72mm apo digitar focus shift?

[Viewmaster]

Hi,

Longtime reader, first time posting. I have a question I was hoping the group may be able to answer. I have a 72mm schneider digitar that I recently got and I'm wondering if it's a good copy.

It appears to exhibit focus drift as I shift to one side using it on a cambo actus/fuji gfx setup. I set up a test where I'm outside focusing on a fence maybe 100 ft away for my central shot, but when I look at the shots that are shifted to the left, it appears the focus has drifted to an object maybe 30 ft in front of the fence and the fence itself is now out of focus.

I've also noticed the lens seems very easily prone to flare or something where it appears to soften parts of the image. Something seems off, but it's hard to reproduce.

Does a decentered or other misaligned element in the lens sound like it could cause this focus issue?

Trying to figure out if I have a bum lens or not. I'm on a mini view camera setup, but I image the tech cams would be able to produce the same problems if it's common. Any thoughts would be appreciated.

 

[vjbelle]

First of all make sure that your front and rear standards are aligned with each other. A slight difference should not make much of a visual difference. You should be able to slightly swing the front standard while at the pixel level and see how your left hand side reacts. But..... that will also have an effect on the right hand side..... one comes near and the other goes far. The best way to check for parallelism is to use very accurate bubble levels. I bought a couple of machinists levels when I started out on my quest. What you are describing, though, sounds more like the 72 being de-centered which is almost always, from my experience, been the fault of the copal shutter not being perfectly plumb. I had to have three of my Digitars repaired by Schneider for de-centering issues. In all cases the Copal was replaced under warranty. If your lens is less than three years old it should be covered for warranty issues. If warranty is unavailable then I would suggest that you may want to contact Grimes who should be able to check if your Copal is not perfectly flat.

Good luck.....

Victor

Edit: I mention Grimes because Schneider is very proud of their Copal Shutters and will charge lots more than Grimes for the exact same shutter....

 

[danlindberg]

I use the Alpa Helvetar 75 (on a Credo 60 back) which is the same lens as a Schneider 72. Mine is amazing and is one of my long time favourite lenses. Razorsharp cornor to corner, shift without degradation whatsoever up to 10mm. 12mm is fine, 14mm you start see softness. My copy is flare resistant! Beautiful lens :thumbup:

 

[TimoK]

As vjbelle said first look that the front standard is aligned. The second possible reason for misalignment is the installing the lens to the lens plate. If you have the lens in Copal shutter, there is maybe a little knob or screw what should to be set into one of the four small holes around the lens hole in the lens plate. Otherwise the lens will be missaligned.