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The Leica M3 was a revolutionary design. It had a combined rangefinder and viewfinder, with parallax corrected frames that matched the focal length of the mounted lens automatically. The viewfinder was the brightest ever made. The M3 was the first camera with an advance lever, instead of a knob. It had a rear door that swings up, to make film loading easier. It featured a new and patented bayonet mount.
The camera became a huge success. During its production time, 215,944 chrome cameras, 3,010 black paint cameras and 144 olive paint cameras were produced in Germany. The Ernst Leitz Canada factory, based in Midland, Ontario, manufactured another 7,080 cameras, presumably all chrome. Total production of M3's was 226,178. Production ended in 1966.
Attention: The M3 was called M3 because it features three focal length frames in the viewfinder: 50mm, 90mm and 135mm. The later released M2 was called M2 because it was a simplified (but yet updated) camera, which still had three frames in the viewfinder! The M2 will have its own article on johanniels.com, just like the M4 has.
You can mount a 35mm lens on the M3. Leica-made lenses that were designed for the M3 have 'goggles' that impose the 35mm view on the 50mm frame. Another trick when you want to mount a non-Leica lens without goggles: stick a piece of black tape over the middle window and use the whole viewfinder image as a 35mm frame!
The M3 has a 0.91X viewfinder magnification. It is the largest magnification Leica ever made in viewfinders. The rangefinder spans 68.5 millimeters. The camera has an Effective Base Length of 62.33 millimeters. (The formula to calculate this: RF width X magnification = EBL)
The M3 excels at the focal lengths it was designed for. You want to focus a high speed lens like the Leica Noctilux 50mm f1.0, the Canon 50mm f1.2 or the Konica M-Hexanon 50mm f1.2? Or the spanking-new Voigtländer Nokton 50mm f1.0? Get an M3!
Ofcourse you can mount 35mm and 28mm lenses, but you will need an auxilliary finder to slip into the accessory shoe. Using a flash on that shoe means attaching it to the camera with a flash cable, there's no hot shoe on the M3.
The M3 has brass gears. These gears were made to fit by the factories workers before being installed. In the later models (M4-2 and later) the gears were made of steel, to allow for a motor drive to be installed. By that time, Leica had also adapted the more cost-effective Japanese assembly method of 'fit or replace', i.e. during assembly, parts were swapped out until they fitted instead of being made to fit. The M3 is a very smooth camera to operate due to the made-to-fit brass gears!
Design changes during production
First production cameras had no frame preview lever. Seeing other frames in the viewfinder was only possible when the matching lens was mounted. Starting with nr. 785891 in 1955, the frame preview lever was mounted on all M3's.
Early cameras had a glass pressure plate. In later models, this was changed to a metal plate. Opinions differ as to the use of the glass plates. Some sources claim Leica took to glass plates because they were worried that rewinding the film might produce static electricity on the metal plates, which would discharge in small sparks, resulting in white spots on negatives. When this proved to be an unfounded fear, they changed to the metal plates. Other sources suggest it's all just the other way 'round, the phenomenon occured on the glass plates and Leica took to the metal plates to avoid it. I have never seen an negative with bright spots on it due to electrical discharges from either pressure plate. Anyway, it would take very cold weather and outdoor rewinding to create static electricity to begin with. Change occured at nr. 844001, in 1957.
Early cameras had 'Buddha Ear' strap lugs. The rivet holding the lug to the camera is put through a little lob at the bottom of the lug. Later cameras had the far more common 'normal' strap lugs.
The bottom plate started out with a bigger 3/8th inch mounting screw, later changed to 1/4th inch.
The shutter speeds started out with B-1-2-5-10-25-50-100-250-500-1000, but later changed to the more mathematical-correct progression B-1-2-4-8-15-30-60-125-250-500-1000. Change occured at nr. 854001, 1957. Keep this in mind when buying a meter for your M3!
The early edition M3 had some design specifics that changed in later M3's. Engineers were uncertain how much strain the gears on the new lever-wind mechanism could take, so they designed a Double Stroke mechanism. First stroke transports the film, the second one cocks the shutter. The process can also be completed with a series of short rocks instead of two complete strokes. Once cameras were in use for some time, Leica repair techs found that the gearing showed no wear at all, and a Single Stroke mechanism was introduced. Change occured at nr. 915251, in 1958. Subsequently, many DS-type M3's were converted to SS-type M3's at the factory. Compentent repairmen can still perform the conversion today.
Modern times: repair and buying checklist
The majority of the M3's is in need of service after 50 years. Even if you manage to buy a camera that is working fine at this moment, you should be aware of this. Compentent repairmen in the Netherlands charge approx. EUR 200 for a CLA (Clean, Lubricate, Adjust). Any additional work and parts are extra. There's also a number of competent repairers in the US, and most certainly in other countries as well.
Expensive repairs are those to the rangefinder system, which is the most complicated in the M3. When buying a 'new' M3, checking the rangefinder system is easy: look through the rangefinder window, both from the front and from the rear. You should see an evenly colored image. Lighter or black areas indicate one of the mirrors in the rangefinder system is in the process of de-silvering. Point the camera with the rear to a bright light source and look through the rangefinder-patch window (the small window at the front left hand side). Again, this should be clear from any 'debris' in the image, the image conveyed from the rangefinder window to the viewfinder is passed on by small glass prisms which are painted black on the ouside, 'debris' indicates that the paint on the prisms is flaking, causing the rangefinder patch to flare or lose brightness.
Other checks to perform when buying an M3:
Check if the rangefinder image lines up correctly. Mount a lens and set distance to infinity, point the camera to a distant object and check wether the rangefinder lines up correct. If off horizontally or vertically, not to worry, this can be adjusted with the CLA. Perform the same check for a closest focus image.
Check if film transport is even by cocking and releasing the shutter a few times.
Check all shutter speeds. Start with the slow ones, cock the shutter a few times and release. One second up till 1/15th second should be clearly distinct, slow gears (buzzing sound) should release evenly.
Remove the bottom plate and lens or body cap. Swing up the back door. Cock the shutter. Point the camera to a bright light source and look for any pin holes on the curtains. Release the shutter and check the second curtain as well!
Cock the shutter again and inspect it from the front, you should see no creases on the shutter but a smooth cloth. Do not touch it with your fingers. Release the shutter and inspect the second curtain.
Check if the take up spool is in the camera. I know, this sounds rather daft, but it's quite impossible (i.e. expensive!) to find one without a camera!
Check whether the frame counter advances. I have owned a camera on which it didn't, and its a PITA since you always need to carry a spare film and run out of film when you're busy or not expecting it.
Have a look at the insides of Leica M cameras.
A Collection of videos on the Leica M3 on Youtube.com