I think the "Jitter sharpness" of fine details, with sometimes double-like looking features, comes from that for example leafs are just outside of the sharpness zone. When then applying slight sharpness, it comes to these double contours, that look a bit jittery in its appearances.

By the way, very common phenomena with lenses that have several aspherical lens elements. When you look at details located at the border, they sometimes look sharp but not entirely. Like a double outline of details. Quite often the case with Chinese lenses, but also some Voigtländer lenses (for Leica M), but also with Leica M lenses not totally uncommon these days: Nowadays almost all lenses Leica brings forth, have aspherical lens elements. With similar effects when details are just outside the sharpness zone - those details look sharp but kind of "double".

This phenomena wasn't present in the lenses from the 80s, because back then not all of them had aspherical lenses.

Well, that's my take on the whole "jittery" fine details thing.

Wide open aperture ƒ5.6

When I use the Pentax 645 FA 150-300 mm ƒ5.6 IF ED at wide open aperture ƒ5.6 - the finest details are not totally sharp. It is more like a soft sharpness, with some faint glow in the finest details. Once you stop down, it all gets sharp without glow.

I am actually impressed that the zoom can be used at wide open aperture. That is not something you often can recommend with vintage mediumformat lenses. Whose performance often was sub-par at wide open aperture. Once stopped down, they really shine with crispy fine details.

However, I like the more blurry background when i use a lens at wide open aperture. And for my Diary images - well they look sharp even if the original at 100% isn't super duper sharp. It does not matter. Yes, I know - I LOVE sharpness. I love when lenses perform well. But that doesn't mean i avoid taking photos at wide open aperture, where they might not be optimal.

Rules and rules

I kind of use wide open aperture anyway... But at least i want to know how lenses perform at different stages, apertures, and situations. They strength and weaknesses.

It is good to learn the rules. And THEN LATER - you know learn to know when or why you break them sometimes. Not because of the principle to break rules by default. Bah. Yeah. Kind of. That's not the art ! But because you know what you want to achieve in a photo, the why. That is the difference. At the same time you have a fundament / ground in your backhand - an orientation - the choice to to go back to the basic rules. Instead of being totally lost in the end, confused form all the alternatives, choices and "bail out" decisions. It is not bad to learn rules in a profession. They are a fundament. Like childhood is a fundament of a human being and adult. You then have the free choice to do things differently. How you might want to. Rules are of course not meant to lock your mind down for ever. See it a little bit more of an investment. From there you can choose different directions - freely.

And sometimes you want to give "coincidence" a leeway to do the choices for you in photography. That really fun too. Especially when you already know the basics by heart - then you can at least avoid the most stupid decisions resulting into blank film rolls.

I sometimes loved to uncontrolled photography. Or uncontrolled double exposures. By letting go and let your "spirit choose the combinations". And see what happens. Yeah, even that, I do too.

Maybe i should do that more often. (Especially with negative film, I find that exciting)

Lens support

Now that I use that new telephoto lens support - i must say the whole arrangement reminds me very much of the handling with the Mamiya RZ67 lenses on the Fujifilm camera, all placed on a rail. Looks and feels a bit bulky (yet also fun, and of course works is slower).

None of those are just "going in park and shoot, type of lenses. At least not this way. I wonder how that lens feels on a Pentax 645N film based camera with AF ? Would I use it free hand ? Perhaps in very good light, I would. Otherwise not.

Then there is also the question of the (relatively soft) mirror bounce in the Pentax 645N camera... Will it be dampened enough, resulting into sharp images with this zoom at 300mm ?

Maybe. Maybe not. I don't know.

Yet.