I must be jinxed. I did a film test with my two M bodies - an M4-2 just overhauled from Sherry, and a like new M6TTL gotten on trade. The test was for linearity of the RF and focusing accuracy.

I used the 90 M-Elmarit wide open at 2.8, with electronic flash from a tripod at just over 1 meter. The M4-2 focuses about 1 inch behind where the RF patch says is in focus, the M6TTL focuses about 1/2 inch in front of where the RF patch says is correct.

Deep sighs... has anyone else had this sort of problem, or tested their own RF accuracy wide open very close?

Thanks in advance....

-- Charles (cbarcellona@telocity.com), May 21, 2002

Answers

Yes - same problems and not at all uncommon. I would repeat the test at 3 and 5m as well and see if it's a consistent infront /behind error. If it is you can rest easy as a very simple tweak of the slotted screw in the roller cam will set it right. Either look on Nemeng FAQ and do it yourself or get a Leica tech to do it for you. If its not the same at different distances you have a bit more adjustment to do which is very fiddly and really requires multiple practical film tests or again a leica tech with a colimator and other special setup jigs. Leica RF focusing accuracy relies on the position of the rollercam to be accurte to within tiny fractions of a mm in relation to the film plane and over time and/or as a result of knocks and vibration things can drift out of alignment.

-- Johann Fuller (johannfuller@hotmail.com), May 21, 2002.

Oh and do the same test on another lens as well - although logic would dictate the same error would occur in both bodies if a lens were faulty it's good to rule out as many factors as possible when trying to solve a problem!

-- Johann Fuller (johannfuller@hotmail.com), May 21, 2002.

I seem to remember that the Leica RF accuracy (0.72 X) spec is about +/- 1/2 inch at ten feet (close to 3 meters). However, when you try to test the accuracy, you really need to be very careful, since it does not take much of a focussing error to be 1 inch off here or there.

-- Eliot (erosen@lij.edu), May 21, 2002.

Charles; see if the rangefinder patch aligns with the lenses you own when viewing an object effectively at infinity.This is an object say at least 1500 feet away. If the rangefinder's patch is aligned at infinity; then the cameras roller cam is correct for that lens when used at infinity..the roller cam is on an eccentric; which is rotated to align the infinity adjustment.....It is fairley easy to do.....

The close adjustment is abit more difficult.What it does is change the gain/tracking of the rangefinder patch movement versus the lens cam movement...When the cam roller's pivot arm length is set correctly; and the infinity adjustment is redone; the rangefinder patch will track correctly with the lens focus...

The length of the cam's roller arm is either lengthed or shorted; and the infinity (roller cam ) is adjusted; then the system is checked..The 2 adjustments are inter-related

-- Kelly Flanigan (zorki3c@netscape.net), May 21, 2002.

The cam arm length is by an eccentric at the pivot (instant center for you mechanisms engineers!). One must loosen one screw and slightly rotate the eccentric to lengthen or shorten the arm.. My Ebay beater grade M3 arrived aligned at infinity; but was off progressively as one took closer photos...This probably is a common problem; because alot of people do the infinity adjust; but less do the full adjust..

I set up my Noctilux for my M3. It took 5 iterations to get the Noctilux spot on.

I shot several photos close up at 1 meter; 6 feet; 3 meters..plus infinity... I varied the cams arm length to three different settings... First was longest cam length; next was middle cam length; last was shortest cam length..

The best of the three was a toss up between the mid and short lengths....Next roll was with a position I called mid-short cam length...Focus was way better at all positions; but still off a grunt..on the steel tape focused upon at 45 degrees to the lens...Place a pencil and aim it at the focused upon inch or cm mark....When way misfocused; one cannot read the rule at F1.0

Next roll was called mid short short..I moved the eccentric just a mini tad or one micro grunt ...Now the focus is good at all distances; when the Noctilux is at F1.0 Kelly

-- Kelly Flanigan (zorki3c@netscape.net), May 21, 2002.

This sounds like something I'll leave to Sherry - I just got the camera back from her about a month ago (M4-2). Maybe I can get her to do both cameras in her less than 5 weeks turn around (she is so far behind she cannot see daylight!)

-- Charles (cbarcellona@telocity.com), May 21, 2002.

Charles; sounds like a wise move! But please check the infinity alignment as a good measure on several of your lenses...One maybe a bum..Kelly

-- Kelly Flanigan (zorki3c@netscape.net), May 21, 2002.

Infinity alignment is aok with every couples lens I have, of both Leitz and C/V manufacture.

-- Charles (cbarcellona@telocity.com), May 21, 2002.

couples=coupled

-- Charles (cbarcellona@telocity.com), May 21, 2002.

The 'infinity test' is not a reliable test for RF accuracy - if the flange to film dimension on the body is out of spec ( Hexar???) or as I have observed even on an M !!! it is possible for the infinity to be out but all other distances under this to be correct. Also setting up the infinity on such an out of spec body will ensure all other distances are incorrect. That is why a practical film test or a proffesional setup is the only way to be sure. Relience on the infinity test could have you 'chasing your own tail'!

-- Johann Fuller (johannfuller@hotmail.com), May 22, 2002.

Both cameras focus with the RF correctly at infinity, and the images are sharp at infinity (wide open). Its the close ups that are off

-- Charles (cbarcellona@telocity.com), May 22, 2002.

This would point to the problem being confined to the RF arm length as kelly described. Get your tools out or get your wallet out!

-- Johann Fuller (johannfuller@hotmail.com), May 22, 2002.

Charles, what is the DOF of the 90/2.8 at that distance? It seems like it must be pretty close to an inch or so, which would sort of cover you on the out of focus thing. 1/2 inches is not very much, IMO.

-- rob (rob@robertappleby.com), May 22, 2002.

When I last aligned my M6 with my 50 f2 at 1m - on TMX I could see a fall off in sharpness about 5mm each side of the focus point. So I think DOF was much less than 1 inch and therefore it will be even smaller with a longer lens. If you have a precision instrument like an M it seems pointless to not have it bang on accurate and you need this accuracy to get the full potential out of the lenses. What's the point of an expensive watch if it run's slow ? unless it's just for show - people don't hang expensive cameras round their necks just for show.........or do they?

-- Johann Fuller (johannfuller@hotmail.com), May 22, 2002.

Rob, my claim of about 1/2 inch on the M6TTL was past the dof, as observable on the scan of the negative. The M4-2 was a good 1-1/2 back from the dof, using the same empirical method of evaluation.

-- Charles (cbarcellona@telocity.com), May 22, 2002.