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Modified 1-Jun-12
Created 31-May-12
14 photos

This gallery shows test results on the phase detect AF system of a Nikon D800E with 24-70 f/2.8G at 50mm and f/2.8. For all images except 10 and 11, the camera was 2.5m from focus target, on tripod. Mup release mode was used. Lens was defocused at infinity before each shot.

For the test setup used in images 1 to 8, the ruler was positioned at 45 degrees, with the 15cm mark in the plane of the focus target. The book on the left was 25cm in front of the target. The book on the right was 25cm in back of the target. Images 1 to 4 are full frame JPEGs, converted from raw in ViewNX. Images 5 to 8 are screenshots from the x0.5 display in View NX. The first image in each pair was taken with AF Fine Tune off, the second was taken with AF Fine Tune at -20. No sharpening or processing was done to these shots other than what is done by Nikon's Standard picture control. I am not showing the shots made using the right AF point. The results are very similar to what I saw with the left AF point.

Observations:

With AF Fine Tune disabled, the center AF points of this D800E produced larger focus errors than the center sensor in the D800 that I tested earlier. But the focus errors on the D800E were were more consistent across the left, center, and right sensors. The D800 had larger errors from the sensors on the left. The D800E showed backfocus errors from all sensors. At 50mm focal length and 2.5m target distance, the best results were obtained with the AF Fine Tune adjustment set to -20 (the negative limit). This was confirmed by testing in Reikan FoCal software. With Fine Tune at -20, the outer sensors were still back focusing, both showing roughly the same error.

When I ran FoCal tests with the lens at 24mm and 70mm, the best Fine Tune settings were 0 (the Nikon default). With such a large variation in optimum Fine Tune settings for the different focal lengths, I am tempted to send this camera and lens to Nikon for evaluation.

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