So, it seems like the Canon EF 135/2 L lens, works well optically when using it at wider apertures. As well with auto correction enabled when you open the RAW file in Photoshop. The image above is unaltered, so there was practically no shading visible in the corners (after auto lens correction).

The photo looks boring - free from vignetting kind of "flat" plus the motive itself wasn't very creative. [it was just a test to see if the AF could lock on Sal's hair. 1 of 3 was in exact focus. The others kind not exactly. But it was low light, and the relatively low contrast on Sal's hair, gave difficulties in locking the AF. And it was a handheld photo at ISO 3200 originally.

In reality of course, the lens does vignette. But the auto correction profile for this lens, eliminates it in Photoshop. Only when you stop down much further - then there is a hard vignetting (in the extreme corners).

The AF is not foolproof, as i already indicated.

Whether that is contributed to the Finger EF-GFX adapter or the Fujifilm GFX 50s II camera itself, with its only contrast based autofocus - I don't know. I assume it is the camera with this combination: because even with native Fujifilm GF lenses, the camera occasionally misses the focus even in bright light !

That has happened more than once.

Now, when the images are smaller like in my Diary - the quality of the lens turns out excellent and sharper. I wouldn't buy this lens, just to adapt it to the Fujifilm GFX camera, though. I mean, I would always strive to buy the native GF lenses instead. They are still the best / most reliable ones.

One. Two. Three.

But since we / I photographers often have other lenses from other brands - a thought comes to mind, why not using them on cameras that are not originally made for ?

In relative terms, i would say the Canon EF 135/2 L is one of the better lenses for that purpose - but surely not perfect. I use it, because i have it at home. Optically it is very good despite it's age - which is admirable that it still performs so well !

The "best" lens in that focal length would be the native Fujifilm GF 110/2 lens, of course. Second, the Sigma ART 135/1.8 (EF Mount) lens. Third possibly the manual Samyang 135/2 lens (EF-mount). All three are basically without vignetting.

I have not yet tested...

I have not yet adapted any Pentax 645 or 67 lenses directly onto the Fujifilm GFX camera, other than via the Vertex stitching adapter. Well, the Vertex method is a totally different concept, not directly applicable in this comparison. I also do not have any Pentax 645 to GFX adapter i realize; only a simple one made for for Pentax 6x7 lenses. but i never tested that.

Which I should, given the many Pentax 67 lenses I have. In the portrait range with lenses like SMC 90mm ƒ2.8, then Takumar 105/2.4 as well Takumar 150mm ƒ2.8, and then the SMC 200mm ƒ4 lens.

Maybe those serve well in the studio for example - especially when used stopped down a bit ? I don't have any true Fujifilm GF lenses beyond 70 mm, which equals to just *LOL* 55 mm focal length.

But also the Canon EF 200/2 L IS, a very strong candidate for portraits with the GFX. I just have to be very precise with the focus and not rely on AF (because it can easily fail, and destroy the image if the focus is 2 cm off, e.g. such as missing the eyes.

Ah. Option. Options. The bittersweet delight of options. Sometimes i suspect that too many options ain't good. We used to be better with the few lenses we had - and worked hard on making the best out of that ?

At least; it gives birth to more creativity.

The Vertex Stitching Method

Originally over a year ago, when I bought the Fujifilm GFX 50s II camera, it was never my idea to use it directly "as it is" straight; e.g. with the sensor size "as it is". Instead the idea was primarily to use it with the Vertex stitching adapter, in order to make true medium format images, by using the FULL image circle from Pentax 6x7 lenses. Or in truth; the results are equivalent to a 7x7 cm "sensor". Even larger than the classic 6x7 negative size.

It is really cool to work like that. You get the exact "fingerprint" that of the original medium format lenses. As if you would have a true 7x7 cm sensor, which utilizes the Pentax 6x7 lenses 100%. Which includes also their optical character for example.

But i don't seemed to have gotten my ass out of the house, with tripod and heavy glass and the whole Vertex setup... That's the main problem - no, the main challenge. Or shall I call it for what it is; the lack of discipline ?

I somehow got away from the original Vertex Rotating adapter + Fujifilm GFX + Pentax 67 lenses idea.

Instead

I used the Fujifilm GFX "as it is", with both Fujifilm GF lenses, as well adapted lenses - directly handheld, without even a tripod. And the built in stabilization is better than i expected. Not as good as the leading fullframe cameras - but good enough to make a difference. To my surprise, I may add !!

I also realized that what comes from the 51 MP sensor, is more than enough. I mean for what I am doing. Even for printing, it is way more than plenty, really. Given that the Vertex method results in an equivalent to a 150 MP 7x7 cm sensor. Which is even more over the top. I will in the future restrain the size a bit, perhaps to 75 MP instead.

Minimal DOF (Depth of Sharpness)

Since i took the photo of Sal at wide open aperture ƒ2 - the depth of sharpness is truly minimal. It puzzles me every time, that the DOF with the somewhat larger GFX sensor often feels slimmer than on fullframe. It might be psychologically. but when I stop down a lens with the Fujifilm GFX - even stopped down to ƒ11 - the DOF is far less than expected.

Kind of strange.

Imagine you would have a true 6x6 cm sensor. Boy it would be finicky; extremely challenging - and i suspect such a large physical sensor size would bring out more disadvantages (in real life) than bringing advantages. It often hits me, how small the DOF is when working with the GFX camera, already. Now think of a 6x6 cm sensor, which is even a lot bigger than a Fujifilm (Sony) GFX sensor.

Both lenses exhibit minimal depth of sharpness.

Of course, I also have to remember, that when I use a 135mm ƒ2 at ƒ2 - the DOF is pretty much as minimalistic like using a 85mm ƒ1.2 at aperture ƒ1.2; razor thin !

Probably less than 1 cm. I stood something like 2.8 meter behind Sal, when i took the photo of him in the kitchen making dinner. Sharpness didn't cover much, due to the really tiny DOF.