One thing occurs to me about how FoCal is capturing images. I think they are using JPEGs rendered with the "Standard" picture control. That picture control uses a fair amount of sharpening which will produce some "fake" detail. You might get more consistent results if you modify the Standard picture control to use the minimum amount of sharpening possible. True, it will probably make the absolute sharpness metrics look worse, but I think the relative sharpness numbers will be more accurate, which would improve the AF analysis. After all, we don't want an analysis based in part on the fake detail produced by in-camera sharpening.