i'm starting out with a black rigid m-50-cron 2295xxx. Its focusing ring is much stiffer than normal so i ask the lens to be serviced by their in-house techician.

First of all, i'm wondering if this lens can be assembled by hand without instruments that are as good as the factory. i mean to ask how close will the lens be to specs, factors like centering and alignment of actual focused distance to the distance marking on the lens. In an SLR, we see the image on screen so we may have a chance to detect these error.

Secondly, i'm not sure of the age of this lens but it may be more than 15 years. i hope to experience what i've read so far that older lenses is less contrasty and present better bokeh. Are these the effect of lens ageing? i'm using this lens with a 0.85M6 for portraits and candids of friends and family, both in- and outdoor. As i'll be using f2-2.8 exclusively, focusing must more or less be spot on, which brings about the first concern.

Lastly, since the lens is already old, i'm less reluctant to use it without any protection filter. But does a filter affects lens performance? "Get good ones, like Leica's" i was told. But i had a chance to look at one and its reflection reminds me of cheapo uncoated filters. B+W looks better. No offense intended. Just telling what i saw.

-- y.shawee (shawee@pacific.net.sg), October 04, 2001

Answers

Most lenses can only be put back together the way the were originally assembled. Any experienced technition can do it-heck, I've even had a few lenses apart and managed to get them back together correctly. Older lenses are not as well coated as the current ones, and they do often have a bit less contrast especially at the wider apertures.As far as filters go, there are strong opinions out there on their use. I can safely say I don't think I ever had a photo ruined because I took the picture with a filter on. Your focusing technique and ability to hold the camera steady when clicking the shutter will have a much greater impact on sharpness than whether the lens had a filter on front or not. B+W multi coated filters are as optically transparent as you can get, and are probably even overkill.

-- Andrew Schank (aschank@flash.net), October 04, 2001.

This lens is the late 1960s (based on the serial number, it was made in 1968). Optically, it is the third version of the 50/2.0 Summicron, which replaced the [legendary] rigid chrome Summicron. This vintage of lens was issued approximately from 1969-1979 and consists of six glass elements, unlike the lens it replaced which contained seven elements. It has an excellent optical performance, said to be higher in optical contrast than the rigid chrome lens.

As far as servicing, in my opinion, anykind of servicing that requires the lens to be disassembled, should be done by a topprofessional, with a lot of experience (eg., van Stelton, DAG, Sherry Krauter). Putting the lens back together is a precision process that requires an optical bench and the proper tools. The slightest mistake could result in decentering etc. of a lens element and loss of performance.

As far as filters, you are correct that Leica filters are mono-coated and reflect a lot of light. I think a multi-coated B & W filter is better, A good filter should not degrade the optical quality.

Good luck with the lens, It should be a very fine performer.

-- Eliot (erosen@lij.edu), October 04, 2001.

If the service being done is simply to smooth the focusing action, they'll probably just clean and lubricate the focusing helical. This is a pretty simple procedure that doesn't involve disassembly of the optical unit.

When you get the lens back, take a few test shots to check the focusing accuracy. Until you've proven there's a problem, don't worry about it.

Regarding filters, do whatever provides you with peace of mind.

-- Mike Dixon (mike@mikedixonphotography.com), October 05, 2001.