So, what is it good for ?

A Closeup lens. Simply said.

From 2-3 meter all the way closer, down to 1.3x macro. I would say that is this lens' primary optimal spectrum. At infinity i feel it sucks. Better buy a good Fujifilm GF lens like 45-100mm, the 110mm ƒ2 or others.

I like the TTArtisan as an experimentell close-up and macro lens. I feel that the Sigma 70mm ƒ2.8 ART is sharper - and at times "in between" it works almost without dark corners, but has them again at 1x macro. Nevertheless, the Sigma 70mm Macro is king in terms of sharpness.

The TTArtisan 100/2.8 2x Macro lens is not as high resolving, but good enough in order to make lovely clse up impressions. And here, i would say lies my primary interest - especially as a mediumformat lens. So, I am of course happy that it doesn't show pesky dark corners in that focus area.

That it doesn't perform so great at infinity... oh what the heck. I don't mind - and will not use it for that either. Nor do i mind that it vignettes at 2x macro - because if i wish to go that super clse - I use my Olympus M.Zuiko ED 90mm ƒ3.5 IS PRO Macro lens which does focus down to 2x (4x Macro) - and does so with automatic focus bracketing.

So. A lovely attractive priced, for mediumformat image sensor useful CLOSE-UP LENS.