Question: 2,8/28mm Biogon and focus range

[leif e]

This may have been answered on the forum before, but please bear with me - I´m confused: Was I fooled? 😱

Point: I bought a second hand, beatuiful 28 Biogon a while ago. At once I wandered about it´s mechanical function when focusing down to minimum focal distance (50 cm, says Zeiss). The focusing on this lens, however, seems to slip, loose contact with camera, let go - whatever. From approx. 65 cm nothing happens at all until the focusing ring stops on the 50cm mark on the barrel. Focussing the other way (towards infinity) it´s the same - first noting until you can feel the focussing "ring" take hold of the lens at 65cm.

When I bought this , I called the guy who sold it. He´d been wandering about the same thing, got an explanation and was told "this was so" or something to that effect. I am possibly easily fooled, but seeing the lens was perfectly sharp and well-functioning in all other aspects, I forgot about it ... Until I sold it myself - to Erik Five who obviously observed the same phenomnon. So; now I´ve gone into researrch modus; is there an answer or is this lens faulty!?🙁

I´d be extremely glad of any answer that´ll make me (and Erik) feel more enlightened.

leif e

 

[thomasw_]

hey leif, what is the minimum focussing distance of your rangefinder body?

 

[leif e]

Sorry - found the answer! It´s due to the difference between the 28 and the others, that focuses down to 0,7m. The 28 must be scale focused from 70cm and to the limit.

leif e

 

[Terao]

I've always assumed its pointless to couple that far down due to parallax and lack of depth of field - a rangefinder just wouldn't be accurate enough. I'm happy to be educated though 🙂

 

[jmi]

FWIW, I find the 0.5m close focus on my CV 21/4 quite useful, since it's easy to guess even wide open at f/4 with this much depth of field. It only RF couples down to 0.7m too, of course. The 28 might be more difficult wide open, but stopped down a bit no problem. IMHO the question should be asked the other way around - why limit us with 0.7m (AFAIK this is the closest any M-mount body will couple, but I'm happy to be educated) on the wides? After all it's just a bit of extra travel on the helical.

The Olympus XA4 is a scale-focus 28 camera and goes all the way down to 0.3m!

In case you haven't guessed I really like the Mamiya C-series TLRs and RB67 bellows feature since it will allow stupidly close focus. Yes the framing is a bit hit-and-miss on the TLR, but so what 🙂

 

[Doug]

I'd prefer the body to couple to the same or closer focus than the lens, as I find it disconcerting to suddenly lose coupling while trying to focus on a near subject. Maybe it's a bad habit, but I'll sometimes just crank a lens to its closest focus and then move back and forth until correct focus is indicated in the viewfinder. Have to watch that with RF lenses that go down to .5m!

FWIW, the Besssa R4 loses coupling at about .6m.