So, assuming I have options, or the Vespid elevates my base, the logical (?) thing is to add the 25mm Vespid MkI ($1200au). It is perfectly sharp from f2.8, especially on MFT or APS-c cams with tighter corners, but has the mild CA issues and wide open gentle softness of the 40mm, so it can be used with character or clean, aside from aperture limitations (more on this below).
This would give me a spread of 25-225mm across four formats (with the IRIX 150 macro), enough for anything I would need, the establishing, group or dramatic wide shot, semi wide two person, several levels of tight and compressed portrait, a true tele-macro and multiple ways of mixing these.
The only flaw in this logic is MFT performance which is half the logical justification for this lens. The 25mm on MFT becomes a handy 45-50mm focal length (depending on camera), but with the need to stop it down to T2.8 to 4 for best performance (maybe, as central performance is decent wide open), it is effectively shooting at T5.6 to 8 full frame equivalent.
If I am buying the Vespids for character not perfection, then the 25 makes sense as, to be honest, the 25 is fine wide open, just not as sharp as the Mk2, better being the enemy of good.
The reality is, my preferred aperture for full frame is T4, where the 40mm is excellent, then at T2.1 it offers a gentler, dreamy sharpness option. In MFT format, T4 is too much depth of field (about T8 FF) and a little slow, so a wider aperture that can be used confidently, like the Mk2’s T1.9 (about T4 equivalent) is better. The Mk1’s 25mm is tempting, but might be a poor saving overall.
In MFT the Hope 25 can provide very sharp and CA free images at T2.1 as well as a warmer image to balance out to cooler GH5s sensor, so I wold basically be buying a wide angle for the full frames, then have a confusing and probably unnecessary choice to make in MFT.
Without it I would not have a full frame wide angle, relying on the MFT 12 Vision, 9mm Pana, or full frame 20-60 S-series etc. I don’t use wides much for video and when I do, AF in MFT format is preferred, so this may be enough anyway (the Vision 12mm is actually really good with insane close focus).
If I assume that my G9II would be the most likely mount for a wide used in “Chivo” style* of super close and intimate, looking for perspective distortion, looking for a too-close feel, the 12mm Vision is perfect and the 9mm Leica provides it with AF. On the GH5s, it is an even stronger effect.
*
If on the other hand I wanted or needed to up that base level, to better support MFT format with more usable sharp wide open speed, go a little wider, have a lens that provides the safety net of even better flare and CA performance, basically no distortion (as a full frame wide), the 24 Vespid MkII ($1700au) is the path.
The MkII’s are more modern optically, often called “mini Arles”, but can be matched to the MkI’s when the older lenses are stopped down.
The 24 is also smaller and lighter, especially compared to the slightly larger than most 25mm.
This of course has the potential to start the whole process again and to be honest, if I had to buy only one set, it would be MkII’s, but I might feel I had missed a trick without a MkI in the fold.
The third option and this is a strange one maybe, is a 28mm F1.4 Typoch Simera, non-C type ($600au), the newer one without that odd locking mechanism, which annoys me when shooting video.
There is breathing and vignetting, but they are optically excellent. I feel the role they would play is much the same as the Vespids, to be the “character” glass,
This would also require two M adapters ($2-500au) and add another mount into the mix, but it would also still be cheaper than the options above and add the same glass with more speed than a Vespid in a smaller size.
A 28mm is not wide, but at this pricing, a 21 or 18 could be added within reason, the whole lot coming in under the Vespid 24’s price.
A hand holdable 28 is very appealing and I am ok with stills lens focus pulling, which has to be balanced with my preferred handling “shape” of the stills lens over a cine lens (backwards to a cine lens).
The head is screaming the 24mm, the heart would settle on the 25, but it’s utility might be limited and my gut is saying stick with what you have. Only the wallet and my perverse sense of running against the tide says Typoch.
*Aka Emmanuel Lubezki the maker of The Revenant.