Update: Good news: Nauticam now makes a MF set-up for the S90 and APS-C. I've been told by Bluewater Photo that there are others who are having trouble with the S90 and NEX7 (no word on other APS-C like the A6000, etc), so MF is a must. It's also the preferred method when working with long macro lens. I mentioned in my above post that I have no explanation why the S90 focuses accurately and fast on my NEX7 when used by itself, but not with a diopter. Given that the NEX7 uses contrast focusing, I'm starting to think the S90's optics are not well suited to diopters and thus never reach the contrast level to lock focus. Just a logical hunch and nothing to back it up (I don't have test equipment). Reef Photo more or less said the same thing in regard to lesser optimized and simpler diopters, thus recommending the SMC-1 for it's superior glass. Unfortunately after buying the SMC-1, it didn't fare any better. Since it's supposedly designed to work underwater, perhaps the S90's focusing will respond better to it there, since all of my testing was on the surface. Still I'm suspect that this will fix the hunting problem. More divers are beginning to use the S90, so in time we'll hear more from others. I was hoping for better after waiting so long for a true long e-mount macro. On the surface, it's a gem and rated higher than the Canon 100L.