It is a lot easier when I use my computer monitor at an angle as a target and sharpness of subpixels as my dependent variable since I can immediately know where the camera focused and eliminate focus variability as a confounding variable. As long as there is no motion blur almost every image for each condition is exactly the same at the same focus point, so it is mostly picking images that focused on the same point.
For images with a flat target it is a lot more time consuming where focus variability is the confounding variable.
First I look through several images in each condition and find some very small feature on which to base the comparison. Then I do a quick crop of that area for each condition and upsize it to 400%. Then I use WS and simply click on that point on each with WS set for 400% enlargement and assign a colors to those sharper than my crop. Then select these sharper images and compare to select a set as possible images. Now from those compare on a second area crop of different detail to try to pick the best one for each condition. There will typically little difference in most of these since they are typically focused at the same distance.
The only reason that this is time consuming is that there will always be focus variability which is why I almost always use my angled computer monitor for initial tests of sharpness.
The attached image is for the two areas upsized to 400% that I used for my comparison of the 300mm f4 with the 50-200 f2.8. First I compared the specific thread detail in the top part of the image and then from the selected set use the crop of the acrylic paint at the bottom of the attached to select the final image.
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drj3
