I have no personal involvement with this offering, but let me offer a couple of thoughts.
"la monture est un pas M26 (comme les Mitutoyo)"
(Google translation: "the mount is an M26 pitch (like the Mitutoyo)").
These Nikon MM objectives have Nikon M26 threads, which are indeed very similar to Mitutoyo M26 threads. However, they are not quite identical. Mitutoyo M26 has a thread pitch of 0.706 mm (26 threads per inch); Nikon M26 has a thread pitch of 0.750mm. These thread pitches are very close, and the number of threads engaged is few, so most Mitutoyo M26 adapters work fine with Nikon M26 objectives. This said, some very tightly-toleranced Mitutoyo 26 adapters might not work. Documentation
here.
"Avez-vous constaté une différence avec des objectifs non télécentriques lors de vos focus stacking ?"
(Google translation: "Have you noticed a difference with non-telecentric lenses during your focus stacking?")
Christophe responded that he has not noticed any such difference, which isn't surprising; for standard focus stacking, telecentricity probably doesn't matter much. Where it may be much more valued is among people doing stack and stitch (macro panoramas where arrays of stacked images at stitched together). I haven't done stack and stitch, so have no experience, here.
In straight stacking, I've tested other specimens of the lenses Christophe is offering, and consider this series of objectives to be worth considering for
some photographers, though not
most photographers.
In addition to telecentricity, they have the advantage (as Christophe wrote) of enormous working distance. The working distances for the objectives in this thread are: 1x--79mm; 5x--64mm; 10x--48mm. Having working distances this large feels almost like cheating.
On the downside, these objectives have modest (though not horrible) numerical apertures (NA), which limits their resolution. Their NAs are: 1x--0.03; 5x--0.13, 10x--0.20. And they are achromats, not apochromats, so there is some chromatic aberration (again, not horrible compared with other quality achromats I've seen).
As noted in this thread, the 1x objective in this series does vignette on an APS-C sensor. However, to eliminate visible vignetting, I only needed to extend my bellows to where this objective was delivering 1.17x on an APS-C sensor. So one might consider it, effectively, a bit tighter than a 1.2x, vignette-free lens on APS-C.
I tested a sample of the 5x in particular on a wide range of bellows draws. I'd have to search a while to find my notes before offering numbers, but do recall being impressed with the wide range of sub-5x magnifications one could successfully use on APS-C, especially if a bit of corner cropping were acceptable. (The figure 2.15x comes to mind, but this may be a figment of fallible memory.) Given the long working distance and small diameter of this lens, I could see it being useful in the field for chasing skittish insects, with either a bellows or a range of extension tubes.
All lenses involve trade-offs, and these objectives offer a set of trade-offs that is definitely not matched to everybody, but may be well matched to some.
--Chris S.
