>>3439437>'cause all my M an M39 lenses have a 0.7 to 1 meter of MFD.That's completely different and a consequence of the lens barrel alone, not even lens formula.
If you put the lens on a bigger barrel, i.e. a longer helical so it can extend further away from the body, it'll focus closer. And you can fit as long a barrel as you want.
The reason rangefinder lenses didn't do that, is because parallax becomes huge with very close focusing distances, so macro ranges are not very usable. And that's why the RF coupling goes up to 0.7m in most RFs, even if you had a lens that can focus closer, you won't see a difference in the rf patch, so you can't focus at those distances using the rf mechanism, you have to measure the distance manually.
In short, because of limitations of the RF viewfinder, lenses were never fitted in long barrels suitable for close focusing, with very few exceptions.
In SLRs you have no such constraints. The only constraint is size, a longer barrel makes the lens bulkier and you don't want that unless you're shooting lots of macro.
And secondarily, even if you stick a longer barrel to focus arbitrarily close, if you want to bring that lens to the market, you have to make sure to design it to have acceptable performance/good in that close range, cause the aberrations change. You can do that by either using a complex floating element design, or by optimising performance for the close range, at the expense of medium distances and infinity.
But practically, you can put any lens in a longer barrel, or bellows, and focus it as close as you wish.
That's how all large format lenses work, and many medium format ones, like for the Mamiya RB/RZ, their TLRs, etc. .
