I had occasion tonight to test a couple of objectives: Nikon CF Plan EPI ELWD 20X NA 0.40 WD 11.0 mm versus a Mitutoyo M Plan Apo 20X NA 0.42 WD 20.0 mm.
To do a quick and dirty flash-to-compare, I pulled both images into Photoshop, layered the two images, and did an Edit > Auto-Align Layers.
Looking around the images, here's what I saw.
Whole frames. I didn't get the two tests framed exactly the same, but they were close.
100% crops, Nikon on the left, Mitutoyo on the right.
Just above image center:
Near lower left corner:
Near upper left corner:
Conclusion is that the Mitutoyo 20X wins hands down. That's no surprise by reputation, but it's nice to see a head-to-head comparison.
Miscellaneous details: Canon T1i, Canon 580EX II flash at 1/16 power with Kleenex diffuser wrapped around the head, Canon EF 55-200mm zoom at 200mm, StackShot at 2 microns, Zerene Stacker PMax with no post-processing. Screen grabs by Snagit.
Edited to add: I tried reprocessing the Nikon stack with skip factor 2, so effectively at 4 microns focus step. Flash-to-compare showed slight focus banding, but I don't think I would have seen it in side-by-side comparison. Theoretical 1/4-lambda DOF at NA 0.40 and 550 nm is 3.4 microns. Same thing with the Mitutoyo produced somewhat more definite banding, definitely visible in side-by-side on careful study. Theoretical DOF at NA 0.42 is 3.1 microns. Conclusion is that the theoretical numbers work OK here.
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