How to check lenses?greenspun.com : LUSENET : Leica Photography : One Thread
A couple of days ago I asked whether I should buy a R4 and some lenses - your responses convinced me..Now I have to meet the man tomorrow and buy the lot (r4 - 24mm f2.8, 50mm f1.4, 135mm f.2.8, 35-70 f.3.5 and a 80-200 f4.5.50 f1.2)..my idea is to shot a roll of film testing the lenses. Get it proceed in a 1 hour lab and buy everything if it seems fine..Its a days journey to meet the man - so when I make the buy there's no going back... My question: how - what to shoot best to see if the lenses are fine?
-- Chris (firstname.lastname@example.org), November 21, 2001
Shooting film is more important to check out the camera than the lenses, that is, to check lens *defects*. To check the lenses, bring a penlight with you. Play the penlight into one end of the lens while looking from the other end at an angle (i.e. not staring straight through like a telescope). You're looking for haze (cloudy, milky), fungus (looks like spiderwebs or snowflake patterns), or separation (looks like a water stain)on the internal elements. Also examine front an rear elements for scratches or fine "wipe marks". Set the aperture to the smallest (22 or 16 or whatever), noting if the clickstops are distinct, and push the aperture lever near the rear element so the diaphragm opens up. Let go of the lever, the diaphragm should spring back smartly. Do this a couple times. Work the focus ring from infinity (it should stop right on the mark, except with mirror or long telephotos)to near distance. It should be smooth--not too loose or stiff, and no binding spots or feel or sound of grit. Check the lens for dents large enough to suspect it has been dropped. With the lens on the camera (or better, a body you know and trust)focus on a sharply-defined vertical object *at least a mile away* and it should be sharp with the lens on infinity.
If you do a film test, use a body you know has a trustable shutter and meter, shoot slide film and use a tripod, otherwise camera defects, shake, and/or printing errors could make you think the lens is faulty.
-- Jay (email@example.com), November 21, 2001.
As usual, Jay has given a comprehensive answer. I would only add that you should examine the screw-heads for any signs that the lens has been dismantled with by an unqualified person.
-- Ray Moth (firstname.lastname@example.org), November 21, 2001.
Man, I wouldn't go the film route. Sorry, I think I know better.
I would try to find a repair shop in the area and schedule a checkout (making sure they have a koritsu tester or another type that measures side-to side variation). This machine will measure accuracy of diaphragms, meter at various EV, and shutter times and curtain side- to side variation. The shop should also have a dial gauge, which measures the lens mount for parallel-ness(?) to the film rails.
Maybe put a roll in the camera just prior and make sure all lenses hit infinity. Check distant details that are harder to resolve (buildings, mountains, etc) and make sure they are rendedred sharp. Don't just set the lenses on infinity, either. Focus on your matte areas of the screen, and carefully.
For one to own a leica and not know it's running specs is ridiculous. someone who doesn't care is probably more proud of their camera vs. their photos.
IOW, Leica's optics are of such quality they deserve to have the best running cameras behind them. Nothing is perfect, I guess.
-- Mike DeVoue (email@example.com), November 22, 2001.
Buying a used lens donít forget to check very carefully a condition of glass surfaces. Check a transmittance of the lens with a flash- light. Refuse a lens with a fungus, a mass of cleaning marks, scratches, sings of downfall.
Shoot against light, it helps you to learn how good is coating of the older lens.
-- Victor Randin (firstname.lastname@example.org), November 22, 2001.