Q&A: focus shift with 50 cron
Last week I received this email:
My name is R. and I’m a photographer in New Orleans, USA. I stumbled upon your blog and wanted to ask a question.
Thank you for writing about the 50mm Summicron lens and posting great photos! I got one of these lenses V5 (the current one) and noticed that when I shoot it at f2.0, my focusing is accurate, but once I go to 2.8 and 4.0, and so on, the lens starts to back-focus. I get people’s ears in focus instead of eyes. Is this normal behavior of this lens? If so, how do you deal with it? I’ve been shooting with Leica film gear for years, but never had a lens do this much back focusing, and if just came back from service.
Thank you and hope you and your family are ok during these strange times!
Thanks for mailing R and I’m still fine, although a lot of my assignments have been canceled.
The phenomenon you describe is called focus shift and it comes in all sorts of variations. In the M9 days I have literally spend days and weeks to ‘check’ my camera and lens calibrations on license plates of cars in the street where I live. It sometimes made me go insane. Here’s a thread on the LFI forum where the problem is described.
Remember that digital is far more critical than film is. You can zoom in on the pixels with one click of your mouse. With film, it’s all much more forgiving.
Lenses and rangefinder can be calibrated to (near) perfection, but focus shift is a ‘natural’ phenomenon that you’ll never completely get rid of. If you can’t live with it, but still want to shoot Leica rangefinders, you can learn how to compensate for focus shift, or use a camera with live view.
For me, critical focus has always been paramount for headshots (I often shoot at 2.8) and I can say the Leica SL has made my life a lot easier.
Don’t give up though. You can make it work with an M9 too.