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My D800 Focus Fix from Melville


Cape Coral, US
5751 posts

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Ferguson Silver Member Fellow Ribbon awarded for the generous sharing of his high level expertise in the spirit of Nikonians Nikonian since 19th Aug 2004
Thu 30-Aug-12 03:50 AM

In case it is helpful to others, here is a record of what I think was a successful repair, but showing how easy it is to interpret it as a failure.

Sent the D800 to Melville UPS ground arrived there 8/14, received it back via overnight UPS on 8/28, two weeks elapsed in shop. I did not request overnight, it was a nice touch. I did contact Nikon ahead of sending and sent pictures, I did not contact them during.

Service was B1, SC 201759, "ADJ Auto Focus Operation" plus usual checks and cleaning.

Arrived back clean, safely packed. I did not get an email that it was coming.

Did some initial shots by eye, looked decent, but to do real testing I used Focal (Reikan).

The good news is left and right far focus were near identical now.

The bad news is that left and right were significantly different from the center, something I've seen commonly reported.

I used Reikan's FOCAL to do a full set of tests on my lenses, starting with the worst case (85/1.4G). I did the tests at both close and far (and sometimes medium) distances, and at max and min zoom, and for the most problematic lenses at left and right point.

In all cases now -- unlike before repair -- there was a nice compromise point that yielded good results on all points. Here is what I ended up using as final numbers, just to show the range:

85/1.4G = 13
14-24/2.8= 10
24-70/2.8 = 9
70-200/2.8 = 2
200-400/4 = 0

Here's a visualization of the problem people may have after the repair. Camera as received, set to zero AF fine tune.

Those are approximately 1:1, left/center/right focus points, with an 85/1.4G at about 1m. Notice the left is pretty much dead on, the right is close, the center is really soft. Please note I didn't test with this image, this is for illustration as I am tired of looking at focus charts.

So let's say I do the obvious thing -- I fine tune the center very carefully. FOCAL calls for about +20.

OK, now the center is pretty good, but both left and right are soft. This is what I've seen reported, and it is indeed true for mine - they are now more symmetric, but they do not match. However, by looking at the curves, I can see that if I pick a middle ground between their respective peaks, I can get visually good for all points. Here is what 13 looks like (which I picked to be the best balance based on FOCAL charts):

To me these are pretty much identical, and pretty much as good as any of the others. It is measurably not quite perfect, but visually I think it is just fine.

I was able to find a happy medium for all the lenses where at different distances and zooms, and different focus points, I got visually good focus.

I could not do that before the repair -- there was no happy medium in several cases. Including on the 85/1.4G. Now there is.

To me it is fixed enough. If you get one back like this - don't expect to just set everything to zero and have it work. And don't expect to peak the center and the left/right be perfect, you may need to look at those separately and pick a compromise. Not desirable, maybe not even acceptable for this price camera - but it works, and while I wasted a lot of time, my focus is now fixed for all of my lenses.


Comments welcomed on pictures: Http://captivephotons.com

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