[adan]

Coming to this thread a bit late - this is the conclusion I've reached, within the past week, after a winter (and in reality the whole 18 months I've had M8's and the whole 7 years I've had Leica Ms) of playing around with various long and medium lenses:

The magic of an RF comes when one can simply, as MarkGay and noah_addis have said, "snap" the two images together once and have a very high - and comfortable - confidence of a focused image at maximum aperture - without having to rack the lens back and forth, back and forth (which is, as Magnum's Dave Harvey put it, a technique for SLRs).

That limit for me is "70-75mm" equivalent @ f/2, at least on those Ms that include the 28/35 field of view (M8 and .72x film Ms). A 75 'cron for full-frame, and a 50 'cron on the M8.

That does not mean that longer lenses cannot eventually be focused. Just that for fast journalistic, documentary reportage, I've put aside the 50 f/1.4 and the 75s and 90s.

Fortunately, a "70-75" f/2 is JUST long enough and fast enough to be a detail lens and a portrait lens and a subject-isolating lens - IF one can get close enough. Which is always the photojournalist's goal (Remember Capa's dictum).

(Part of this past winter was spent playing around with some medium-format film gear, and I was interested to note that a 50mm on the M8 is about exactly equal in framing to a 150 on 120 film, assuming one crops the M8 image to 6x7 or 6x6 shape. And of course 150mm is the upper limit for the Mamiya 6/7 rangefinders, as well as being the most common long lens for many Hassy users.)

So I've come to terms with the fact that just because Leica makes longer lenses does not mean I have to use them, if they are outside my comfort zone. My 15/21/28/50 prime shooting set is very similar to a Mamiya 7 user's 43/65/80/150.

Historically, very few Leica users of note have strayed much beyond 50mm FOV - especially once SLRs became an option. In no particular order - Paul Fusco (21/28/35 on an M and a 180 on an SLR); Jill Freedman (21/35 on an M and 105/180 on a Nikon); Harvey/Meiselas/Webb/Franklin/Salgado at Magnum (28/35/50 most of the time); David Douglas Duncan (28 and 50 on M3's + a 200 on a Nikon for his Vietnam work).

If I really need a 75/85 f/1.4 or anything longer - I'll find an SLR. Thus far I have been able to avoid the temptation through just moving closer.

I started out with a Canon FX SLR that had a split-image prism in the finder. And I've been addicted to split-image ever since (part of what drove me to RFs was the evaporation of split screens in most modern SLRs). My own perception is that the accuracy curves for SLR (split) vs. rangefinder (40+mm effective base) cross over somewhere between 50mm and 85mm (on a full-35mm-frame camera). Aperture plays a role, though. An 85mm f/4.5 setting on an SLR zoom is much harder to focus than an 85 f/1.4 (SLR) or 75 f/1.4 (RF) because the "baselength" of an SLR split-image is essentially the wide-open aperture of the lens.