A handy telephoto lens.
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The Canon 135mm f/3.5 LTM lens.
I profiled the 135mm f/3.5 Canon LTM lens here. I had to do a bit of work to reprofile and extend the cam mechanism for correct focus but the results are well worth it.
Before revising the cam I made sure that the rangefinder was correctly set using the 90mm Tele-Elmarit. The procedure for adjusting the cam follower (roller) is illustrated here. If your rangefinder is not correctly adjusted – and mine was not when I received the camera – then you are simply wasting time.
A 2mm Allen wrench is used to adjust the cam follower.
The 135mm focal length, especially used at large apertures and/or close focus distances, is really stretching the rangefinder accuracy of the Leica M to its limit. In such cases I advocate using ‘bracketing focus’ – one image nearer than seems right, one at the best apparent rangefinder setting and one too far if you want assurance of peak resolution. With digital that’s a realistic approach. With film reckon on $45 for 3 snaps with one sharp one …. Alternatively there are both 1.4x Leica aftermarket viewfinder magnifiers ($250 used) or aftermarket variants ($100) which enhance rangefinder resolution, but having to screw one into the eyepiece every time you take a picture seems like a royal pain. Further, you will barely be able to see the 50mm frame lines with the magnifier fitted and the 35mm ones will not be visible. So removal is the order of the day of you mount either focal length.
How far is ‘infinity’ as marked on the lens? It’s much further than you might think. In the test images below, the car’s registration plate is exactly 82 yards away from the camera, whereas the roof at the top right is 125 yards distant. There is a clear difference, per the rangefinder, between 82 yards and 125 yards. At 125 yards the lens is indeed set to infinity. At 82 yards it is set thus:
The lens focused at 82 yards.
Stated differently, if you want to insure that when the lens is at infinity the subject is also at infinity, your subject must be 125 yards or more distant from the camera. That’s a long way off. At 82 yards and 100% pixel peeping at full aperture the depth of field is no more than 4 feet fore and aft of the registration plate of the car in these images. That’s as good an illustration of how critical focus is with a lens this long, used with a Leica rangefinder, as I can conceive of. It also shows what an extraordinary feat of mechanical/optical engineering the Leica rangefinder is to this day, and has been since the first M3 in 1954.
Here are the test images taken at all apertures from f/3.5 down to f/22 – the lens is coded ‘001001’, where ‘1’ denotes a black paint filled pit. The lens is so distortion and vignetting free that there is no need to use a lens correction profile in LRc when processing images. These images are SOOC, and I used a monopod to minimize camera shake.
Test images from f/3.5 to f/22. The apertures shown are incorrect.
You can view all 8 images in medium size by clicking here.
To view full size 22mb originals click here. It’s a large file so be patient when downloading. You can zoom in on these to your heart’s content.
Conclusions?
- Hard to focus correctly using the rangefinder at full aperture and/or short subject distances
- Mild flare at f/3.5, disappears by f/5.6.
- At f/3.5 the whole frame is usable with a touch on the LRc ‘Dehaze’ slider and will easily make a large print with excellent resolution if focus is correct.
- At f/5.6 the resolution is high across the frame.
- There is little change in resolution hereafter through and including f/22. If there’s any diffraction at the smallest aperture it’s nearly impossible to see.
- Peak definition is reached at f/5.6 but there’s very little to choose between any aperture from f/5.6 to f/22.
- No meaningful color fringing at the edges of the frame at any aperture. The lens is 6-bit coded as a Leitz f/2.8 135mm Elmarit-M which delivers the best result of the three coding options for 135mm lenses in the M10’s firmware.
- There is no LRc lens correction profile available so I use the one for the 135mm f/3.4 Apo-Telyt-M. The only noticeable difference is correction of very minor pincushion distortion, but it’s not really necessary other than in architectural photos taken straight on.
By the way, disregard the f-stop data in the EXIF information. The M10, even with 6-bit coding adapter, does a poor job of estimating the aperture used. (There is no electrical or mechanical link between the lens’s aperture setting and the camera, so Leica estimates the aperture based on the shutter speed and ISO used). Go by the file names, moving the decimal point in the last three digits one place to the left to see the aperture used. So, for example ‘110’ means f/11.
The lens is an outstanding bargain. I paid $120 for mine, shipped from Japan (they are hard to find in the US) and in near mint condition. A 6-bit coded Fotodiox Pro adapter and an odd sized 48mm UV protective filter (New Old Stock found on eBay) added $28 for a total of $148. Not a lot for a fine optic, albeit one which I will use only occasionally. I also had to invest sweat equity in modifying the cam and installing a red dome mounting index, but that’s my idea of fun. It may not work for you, in which case I would look at a good used 135mm f/4 Leitz Elmar at around $250. These are abundantly available. As with all Leitz lenses of this vintage be sure to check for haze, fungus and scratched glass, the latter always thanks to some incompetent who took to cleaning the lens with his soup stained polyester tie.
The 135mm f/3.5 Canon LTM is a fine optic for picking out architectural details and the like and is recommended for its limited specialized uses.