10-16-2016, 11:53 PM
there are 4 different distances to adjust AFMA - with a zoom it's also 4 different FL at 4 different distances, so don't complain- it's only a prime! The way I did it was using FoCal, getting the AFMA values with Nikon and then use one AFMA and calculate the other 3 distances. So, if I got values like -5, -1, 2, -3 at 0.4, 0.8, 2 meters and ∞, I set the value of the camera to -3 (at ∞) and for the rest I used the -3 and compensated the other values. So, in the dock the same row was -2, +2, +5, 0 because I always calculated then with the final value and subtracted that form the other 3. So, it's doable. I also could have put the whole lens to the values, but my aim was one setting without Sigma values, just Nikon values, so I could use it on another body, check the situation at infinity and the rest should be fine.
I admit I didn't check again after setting the lens by the dock, I did that in the beginning to see if Nikon's AFMA value is roughly the same like Sigma's. I found "yes".
With a Canon it should be simpler, because FoCal can do the setting of AFMA automatically. With Nikon, you need to change this value manually. It IS at time consuming kind of a non-creative job, it told me things about my lenses I really didn't want to know just to become insecure with focusing afterwards.
If it comes to focus reliabilty, I've seen all kinds of graphs from genuine and Sigma lenses - and also, the same lens doing a second test and the graph went ballistic or flat. PDAF the way I learnt it, is a guessing rather than a reliable process. And that was with test conditions. Lighting, tripod, shutter pre-release, waiting time between mirror and shutter and a very high contrast target.
If the conditions become worse, you better take a couple of frames and look for the best (if it has to be wide open).
You're right with the other focus points - I realized I'm doing AFMA only for the center point. A little field curvature, a little incorrect adjustment of the AF-modue (which I had with the first D810, I got it exchanged by Nikon (and the other went into grey market, hahaha).
I wish I could say else, but the reliability curves for the 50 mm Art appear to support your findings. Equally worse was the 85/1.4 G. I think, if I took the time and just run enough tests, every lens could have a bad run.
And now, with mirrorless, everything is silky smooth? Not in each situation. BUT: I always can set the manual focus override. Meaning, as soon as I touch/move the focus ring, the EVF enlarges generously and I'll know in advance what's going on with my sharpness. If the object is static, that is.
If it's moving, it's also a guess play, just one withe the higher number of keepers
I admit I didn't check again after setting the lens by the dock, I did that in the beginning to see if Nikon's AFMA value is roughly the same like Sigma's. I found "yes".
With a Canon it should be simpler, because FoCal can do the setting of AFMA automatically. With Nikon, you need to change this value manually. It IS at time consuming kind of a non-creative job, it told me things about my lenses I really didn't want to know just to become insecure with focusing afterwards.
If it comes to focus reliabilty, I've seen all kinds of graphs from genuine and Sigma lenses - and also, the same lens doing a second test and the graph went ballistic or flat. PDAF the way I learnt it, is a guessing rather than a reliable process. And that was with test conditions. Lighting, tripod, shutter pre-release, waiting time between mirror and shutter and a very high contrast target.
If the conditions become worse, you better take a couple of frames and look for the best (if it has to be wide open).
You're right with the other focus points - I realized I'm doing AFMA only for the center point. A little field curvature, a little incorrect adjustment of the AF-modue (which I had with the first D810, I got it exchanged by Nikon (and the other went into grey market, hahaha).
I wish I could say else, but the reliability curves for the 50 mm Art appear to support your findings. Equally worse was the 85/1.4 G. I think, if I took the time and just run enough tests, every lens could have a bad run.
And now, with mirrorless, everything is silky smooth? Not in each situation. BUT: I always can set the manual focus override. Meaning, as soon as I touch/move the focus ring, the EVF enlarges generously and I'll know in advance what's going on with my sharpness. If the object is static, that is.
If it's moving, it's also a guess play, just one withe the higher number of keepers