Oh !

did i mention that the Fujinon GF 500/5.6 OIS is a sharp lens ?

No optical errors visible

Oh, it is sharp. from wide open aperture ƒ5.6 - from the center all the way into the extreme corners. Simply sharp. At all common apertures (until diffraction kicks in if you stop down a lot, say ƒ 16. Which you can later sharpen up anyway, neutralizing the diffraction effect).

While sharpness isn't truly that much super different from the Pentax 645 FA 400/5.6 ED sharpness, where the latter when handled carefully and with exact focus and some slight sharpening really is a sharp lens... Yet, one thing does stand out directly with the Fujifilm GF 500:

There are no optical errors visible.

No fringing. No LoCA and no chromatic aberrations. Everything is crispy and sharp. Which is - let's face it - a true delight ! It also means, there isn't any processing necessary later - because it is all optically correct.

Only Noise AI i sometimes apply - since the Fuji GFX 100 sensor at elevated ISO is slightly more noisy, compared to the GFX 50 series sensor. Either way, both have so many megapixels that noise is never truly an issue.

Acquiring correct AF focus

So far, i feel it is a bit easier to get the exact focus point with the Fujifilm GF 500 lens (on a GFX 100s II camera), compared to the Pentax 645 FA 400/5.6 ED lens with the Finger 645-GFX AF adapter. However, at the same time, it is too early to judge, because I need far more practical experience in various weather, light conditions and photo situations - in order to see and feel the difference between both.

I do get a hunch, that the acquiring of correct AF point - is easier with the native Fujinon GF 500 lens, though. Together with a slightly better image stabilization, allowing sharper images at medium shutter speeds; let's say in the range of 1/20 to 1/60 sec. Here i struggled sometimes with the Pentax 645 FA 400/5.6 ED lens (on Fringer adapter).

Anyway. I get back to this along the road of testing the Fuji 500 lens.