Probably diffraction IS degrading the image quality of all of these shots. The point is that it probably doesn't matter unless you're going to go compare. Ie if I go take that shot of the butterfly and make a 24x36 print from it, and I go take another shot of the same butterfly... oops, I didn't do that. OK if I go take a shot of another butterfly, one at f/22 and another one at f/8, and then print them both at 24x36, yes of course you will see the difference. One of them will have a LOT less DOF than the other. And, if you get over that difference, you will probably be able to see that one of them is somewhat sharper, too - the one without the DOF. You'd have to be looking IN the (smaller) in-focus area to compare, and you'd have to be mentally "masking out" the out-of-focus areas, because they will make the one with less DOF look soft, even though it's actually sharper. IF you do all that mental gymnastics, you will see that diffraction really is real - note that I didn't claim anywhere that it isn't real. But until you see the side-by-side, it doesn't really matter, because with good technique (or luck) you can get a quite sharp result even with diffraction interfering. Whether or not another hypothetically equivalent image might have been better is close to irrelevant if what you got is good enough.
In this case, I was lucky enough to get everything still enough (or any motion hidden enough, by using a flash), I used a top-caliber lens (200/f4 Micro) and mounted it all on a top-caliber tripod and head, so that I got a quite sharp result with appropriate DOF. That last part is crucial: I could easily have simply dialed back to f/8 to get a sharper image, but it either didn't cross my mind, or more likely it did and I did a DOF preview to discover that it was much less of a composition at f/8 than at f/22.
Whether I used a D3, a D7000 or 35mm film really isn't even the prime consideration.
Actually a DX body attempting to make precisely the same composition probably has a mild advantage over the D3 here: because for the same framing, the DX body yields roughly one additional stop of DOF. (Because for the same framing, you'd be 50% further away, ergo more DOF.) Since there's inherently more DOF, you need to stop down one less stop than on FX, thus potentially avoiding a little of the diffraction problem.
I should mention that I make a fair number of 24x36" prints, and by the time I am to the stage of making prints, I pretty much don't pay attention to shooting parameters, etc. I use the whole range of apertures on most of my lenses, so I'd assume that the prints are from a similar range of apertures. (There are some lenses that really perform pretty poorly when stopped down - the 35/f1.4 AIS is one of them - so I don't go there on those lenses. On the other hand, the 85/f2.8 PC looks pretty good at f/45, so I do use that.)
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!