El Segundo D800 and D4 repair results

Started Jun 28, 2012 | Discussions thread
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em_dee_aitch Veteran Member • Posts: 3,675
El Segundo D800 and D4 repair results

I said I would report the results of my D800's trip to the El Segundo facility, so here it is.

I wish I could say they fixed it or didn't fix it, but I'm afraid they did neither, that they made it somewhat better but only "kinda fixed it."

As a premise to explaining this, I would like to mention one of the complicated realities of AF fine tuning that is often left out of these discussions, as it is crucial to my final evaluation: Always remember that a given lens/body/focal length (in case of zooms) combination does not give results at just one singular AF fine tune value. Rather, it will spread good results over a range of values, and we should be looking for the center of the cluster to get best results. This is because, even in the very best examples of Nikon bodies, phase detect AF results will have some shot-to-shot variation (in fact, it's a feature of Reikan Pro to let you measure that variation)... For example, the center AF point with my 24-70/2.8G at 32mm will drop good results from -15 all the way to 0 (fine tune values), so I can see they are clustering around a center of -7 or -8. That premise established...

I initially thought my D4 was OK, and even posted about it here, but on further examination it was somewhat affected by this issue (less so than the D800), so I sent it in with the D800 given that I already had a nice box ready to go.

Both camera bodies tested with the 24-70/2.8G at 32mm and wide open (to avoid any question of stop-down focus shift), so the fine tune values I mention are specific to that particular lens and not a suggestion that the bodies would trend as negative in values with other lenses. However, any good lens should be able to reveal the overall relationship between the AF points.

D800 results:

Prior to the trip, my center and right points matched very closely in AF fine tune requirement, with the left point being about -15 off from them.

After the trip: my center point clusters around -7 or -8; both my left and right points cluster between -15 and -20 (if the fine tune were to go to -25, my shots suggest that the spread of "good" results would fall to -25). What this means is that I could run the lens/body combo at -15, which would give me kinda OK but compromised focus across the entire frame. Is that really the best that D800 can do? I don't really know. I do not feel that at -15 compromise my results are as consistent as some of the examples that people have posted here to prove that their camera is working, but at the same time I don't know to what extent people here have cherry picked their images. The right point clusters about 1 or 2 points more negative than the left, to an extent that is noticeable but not enough to really matter on this particular lens. So overall the results are far more symmetrical than they were originally, which is probably a good thing, but the center and edges still do not agree.

D4 results:

Prior to the trip, was just a less bad version of the D800 issue.

After the trip: With same lens/focal length, the center AF point results were virtually identical to the D800, with the center point clearly clustering around -7 or -8 with good results littered all the way from -15 to 0. The left and right af points were very well matched on the D4 (to each other, not the center) with good results being spread from -20 to -10, but with it looking like the true center of the cluster was probably between -14 and -18. Again given that the fine tune does not allow you to see what -25 would look like, it is harder to see the center of a results cluster when the good results are effectively running off the end of the scale. So with the D4, just like the D800, I have the option to run a compromised choice of -12 or so and am again left wondering "can Nikon do better?"

Oh, and to make this more wonderful: I did something I really did not want to do and re-scrutinized my remaining D3s... and it does the left bad point as well. I initially thought it didn't, but it does. The key issue there is that D3s magnification at 12 MP just does not make it a huge deal, it is not quite bad enough to stress over. It is more visible at 16 MP in the D4 than at 12 MP. And of course it flat out ruins a shot on the D800, if you expect a D800 to produce 36 MP that contain more real detail than a focused 8 MP

In conclusion, the AF points on both of my bodies produce what could be terms "bowed" results.

Sorry, I have not had time to create any info graphics out of my test target shots yet and am extremely busy next few days, but maybe will next week.

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David Hill
San Francisco & San Jose, CA | Austin, TX
Wedding Photographer and Apparent Gearhead

Nikon D3S Nikon D4 Nikon D800
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