Horicon after LensAlign and Focus Tweaks
Black Tern in flight alongside Hwy. 49, Horicon National Wildlife Refuge, Mayville, Wis. | Canon 7D and 400mm f/4 DO IS lens | Exposed 1/1600 sec. @ f/4, ISO 400 (neutral EV)
A Brief History of “Back-focus”
Last weekend I was at Horicon National Wildlife Refuge and experienced some focus problems with my Canon 7D heretofore non-existent, or so I thought. Upon reviewing photographs from the 7D from the past several months, I noticed that none of them were actually as sharp as they could have been. I attributed the softness to the lack of acutance in the files, and while I continue to believe that is an inherent property of cramming 18 megapixels into an APS-C format sensor, there was a real problem in play.
I didn’t want to believe that it could be a question of the camera “back-focusing” (or front-focusing) because I’ve grown to distrust people’s claims that their camera, and not their own inabilities, are to blame for their out-of-focus photographs. I don’t remember these claims from the film days. Perhaps I was just oblivious to the complaints, but I tend to believe that the instant feedback of the digital camera is partly to blame for the knee-jerk reaction that anything wrong with the pictures must be camera, not operator, error.
I will not mince words: ever since the Canon 10D and the Nikon D70, there’s been a lot of bitching and moaning in online forums about back-focused images, and I did not believe them. At all. Until now.
Now, I will argue that there is definitely operator error to blame in most many cases of complaints about back-focusing. Last weekend I was convinced that I must have chosen the wrong focus point or didn’t have the AF locked by holding in the rear button–some prefer AF to only be activated by using the back button, I prefer AF to only be turned off if I hold in the back–and allowed AI Servo (Continuous AF for Nikonians) to screw up the focus. To confirm my assumption, the next day I took test photographs in the garden around my parents house in Racine, Wis. and was shocked to discover that none of them were sharp. Sure, the wind was to blame in a couple cases, but even when conditions were perfectly still the results were poor, so I rented a LensAlign from Lensrentals.com to investigate whether front or back-focus was to blame.
And what did I find after I unpacked and set up the LensAlign? The 7D and the 5D Mark II both back-focused with the 400mm DO IS lens. Well, there goes the neighborhood. And a lot of preconceived ideas, with it.
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