Autofocus Calibration

I only brought one lens to the #MarinPhotowalk on Sunday: a Nikkor 135mm f/2 AF DC, which I bought used a few weeks ago. I shot everything wide open at f/2. But when I uploaded the images, it seemed as though every one of them was a little soft. In fact, the in-focus point was just a bit farther than where I intended, usually someone’s closest eye.

So today I dragged out my MTP LensAlign and checked that lens on my D700, which I also bought used about a year ago. Sure enough the tests were back-focused about 1/2″ at f/2 and a distance of six feet. That may not sound like much, but with that configuration the depth-of-field is only +/-0.36″.

I assumed the problem was just for my 135mm f/2 lens, but no. It’s off the same amount for all my lenses. The good news is (a) it’s adjustable in my D700, and (b) instead of changing it for each lens, there’s a Default setting that applies to all lenses. The range of correction is +/-20. (I don’t know what the units represent.) It took -13 to get it right.

I mentioned this to Scott Loftesness, who wasn’t aware that you can also do this on a Canon 5DMkII. I know it’s also adjustable on my cropped-sensor Nikon D7000.

The Lens Align MkII is way overpriced at $79.95, but it does work quite well. I haven’t seen discount prices anywhere. I recommend borrowing one if you can. BorrowLenses.com rents the Pro version for only $11 for three days. The difference among the models is relatively insignificant.

I previously bought the Spyder LensCal which is a few dollars cheaper, but I sent it back to Amazon because the construction quality was so poor.

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