D800 Far left/right AF issues...

Started Nov 5, 2012 | Discussions thread
Fayard
Regular MemberPosts: 127
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Re: How is this possible?
In reply to photo81, Nov 7, 2012

photo81 wrote:

Right, I understand. When I said a few feet/meters, I mean for a focus target that's maybe 6-10 feet away, similar to your picture setups - so definitely a significant amount. Definitely at LEAST -10 of AFFT compensation.

I realize that something like +/- 10 is "normal", and I'm resigned to the fact that this is what we have to expect from the camera manufacturers these days (at least with Nikon; I don't have first-hand experience with Canon or other SLR brands). My point is that I think such sloppy AF is unacceptable, and something the camera makers need to improve on.

Photo81,

If you go to Lloyd Chambers website, you'll see pictures where he focused 40 meters away and where the focus lands 15  meters away from him. This was done with a 35mm lens at f1.4. With such a wide angle lens, the sharpness of the object where the focus was supposed to land is a little bit affected, but not that much. And most people don't shoot at f1.4 objects 40 meters away from them.

This was done with a D3X, way before the "D800 autofocus problem". Using some targets, I found out that I have "way too much" difference in betweem my AF sensors (8 AF Fine Tune units for a 35mm f1.4, and 12 AF Fine Tune units for a 85mm f1.8). As Falk gives the limit of 20 AFFT for a f1.4 lens and 15 for a f1.8 lens, I guess I am within specifications. Some people have reported a difference of 30 AFFT units, others could not even Fine Tune their lens for some AF sensors. I guess that they are the ones who need to get their body serviced.

Lowering these numbers might be a difficult task. We should also consider that under temperature change, the body might deforms and these optimal values change. A solution would be to get rid of those phase detection focus systems or replace them with systems on the sensor, like what is done on the Sony 99. But, it implies that there is no viewfinder anymore

Anyway, even it the 12 AF Fine Tune difference on the 85mm drives me crazy on a flat target, real world pictures (for instance portraits) are still very good even at f1.8. I even manage to get the eye in focus and the eyebrows slightly defocused with all my AF sensors with a portrait where I can see the top of the shoulders. Not that bad

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