DotTune: AF tune technique without taking photos

Started Jan 31, 2013 | Discussions thread
Horshack
Veteran MemberPosts: 4,143
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Checking for Left AF issue
In reply to Horshack, Feb 3, 2013

The method in the OP can be used to detect whether your body has the D800/E "Left AF" issue and if so, to what extent. You simply repeat the procedure for the Left and Right AF points and compare the results to the center. If they all tune to the same value or within a few AF tune units then your body is good. If both the Left and Right tune to the same value but are materially different from the center then both periperhal points are misaligned or you have a lens issue (the new Sigma 35m f/1.4 has this issue on Nikon FX bodies btw). If the Center and Right tune to the same values but the Left is materially different then your body has the Left AF issue.

For maximum comparative accuracy I suggest setting up three identical AF targets, each positioned over their respective AF point. The targets should be at least 5 feet away and parallel+equidistant to the camera body. You can confirm this positioning by entering LV and establishing critical focus on the center target, then zooming at the right and left targets to confirm they are in focus as well. Keep in mind the peripheral targets wont be as sharp as the center, but they should be sharp to the lens standard and equally sharp to each other, provided your lens is not decentered.

It's best to use a lens that is 50mm or less in focal length, the wider the better. The 24G and 28G are the best lenses to use.

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