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snapsy wrote:
You post this same incorrcect information to every tuning thread. The fact is AFMA is very precise and thousands of photographers have used it successfully. Additionally, Nikon uses the same mechanism as DotTune in their new automated AFMA mechanism in the D5/D500, which is very precise if you perform their function multiple times on the same locked focus and average the results. This multiple invocation is required because Nikon's automated implementation doesn't perform the multiple phase-detect cycles that are part of the DotTune procedure.
Korben, the reason you're likely getting different midpoint values for each test is due to variation of your focus step. For optimal results I would suggest either manually focusing in LV at 100% magnification using an optical loupe or using a target with 3D references for precise focusing. This is because Nikon's implementation of contrast-detect AF in LV is not very precise. Another thing you can try is to perform multiple DotTune operations on the same locked focus, which will eliminate focus variability from the equation and establish how good your target, lighting, and your viewfinder confirmation evaluation is.
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You are misunderstanding me I think. He's getting a value of -19 on one end, and +4 at the other - using a midpoint of -7 or -8 is nowhere near precise. The only precise way to do it is currently impossible, which would involve a separate value for every combination of FL and distance. Nikon's automated implementation does not solve the problem either except for a single data set. If you have to max out AFFT to fix your lens at any combination, you should be exchanging it because you will never zero it out across the entire range. Further, if you have to settle on some middle-ground value that makes your lens OK everywhere but never great, that's not a proper solution either. Viewfinder 'tuning' has been around since the D3 in 2007 and it has the same problems today as it did back then. Until Nikon opens up more data points, you're always going to be better off exchanging the lens for one that requires no AFFT. Sigma has the right idea with the dock, but even that is an extremely painful process.
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