"Reikan FoCal Pro for D800 Multi Point Focus Test?"
St. Louis, US
anybody using Reikan FoCal Pro for Multi Point Focus Test on D800? I think it's a great tool (probably the only one available to the public) to test Multi Point AF in a more scientific and objective way.
I did only some initial test and need to spend more time with the software, but what I am wondering is what would be the statistical level of significance to classify an AF point as showing significantly lower accuracy than the average.
What this software can do is to test each of 51 AF points at different fine tuning AF adjustment levels (from -20 to +20) and then assign the recommended AF fine tuning value to each of them. From the chart one can read the exact values assigned by the software to each AF point, so let's assume the central AF point needs "0" AF fine tuning and the far left AF point needs -20 (or more?) it would be probably a significant discrepancy in AF performance and the service of the camera tested would be probably necessary.
So, I am wondering how to use the software in the most proper way to check all 51 AF points performance consistency.
I would imagine at least 2 ways to do it: 1. First do Automatic Autofocus Microadjustment (not really automatic with D800, because one needs to manually change the AF fine tuning values during the test, which is not a big issue). 2. Then perform Multi Point Focus Test for just one Single AF Microadjustment/Fine Tune value, which has been determined by Automatic Autofocus Microadjustment in point 1. In other words we first let the software choose the optimal AF tuning value for a given lens and then with this value set we test all 51 AF points for their consistency. If some of them need significantly different AF fine tuning value it may mean that the camera needs to be sent for service. Ideally it would need to be done with at least 2-3 different lenses.
Another way would be to perform Multi Point Focus Test for the whole range of AF fine tuning values (e.g. -20, -10, 0, +10, +20) and let the software determine the best AF tuning values for each of 51 AF points. Then we would need to assess the statistical significance for the range of AF fine tuning values suggested for the software, so for example if the software finds out that we have some AF points, which need -20 and some other, which need +20 it would be definitely very significant range, so the camera would need to be sent for service. Again, ideally it would need to be done with at least 2-3 different lenses.
Anybody with similar thoughts/experiences?
I am planning to perform a series of tests tomorrow to find out how consistent all the AF points of my D800 perform. Based on the results I will decide if I want to send it to Nikon for adjustment, or not, but I am still wondering what would be statistically valid significance values for this kind of testing.
#1. "RE: Reikan FoCal Pro for D800 Multi Point Focus Test?" In response to Reply # 0
St. Louis, US
further to what I wrote yesterday I spent almost the whole morning testing both my D800 and D4 with Reikan FoCal Pro to see how different AF points perform and what is the variance between them.
The most interesting observation is that the average Quality of Focus (QoF) for any of D4 AF points is much higher (about 20%) than for D800, all other factors being the same (same lens, same target, same distance, etc.) Another interesting finding is that the variance for QoF among 51 AF points in D4 is significantly lower (about 20% again) than in D800.
It seems that the AF points, which can almost always be relied on are the 9 central ones. The other AF points show much higher discrepancies, depending on the lens, distance from the target and lighting.
In general it seems that the variance between 100% QoF for the best AF point and about 50% for the worst one is pretty common, regardless of the testing setup, which really surprised me, because I expected much more accuracy and consistency.
Anybody performed the same tests with Reikan FoCal Pro? I would like to hear about your results.