Introduction
The Leica M rangefinder is one of the most recognizable cameras of all time. The original M3 is a hallmark of industrial design, and by popular opinion was voted the greatest gadget of all time by eBay UK and Stuff Magazine, topping the third-generation Apple iPod and even the original Sony Walkman. The literary James Bond used a Leica M3, and Alberto Korda created the iconic Guerrillero Heroico with a Leica M2. There's no denying that the Leica M has played a significant role in the 20th century. There have been various iterations of the Leica M, and its basic design has remained largely unchanged for sixty years. So what sets each one apart?

M3 (1954-1966)

Introduced in 1954, the M3 was the direct successor to the Leica III. Notably, the M3 featured the new M bayonet mount, which has remained virtually unchanged to this day. The M3 is instantly distinguishable from other M cameras from its prominently bordered windows. This camera is notable for combining the rangefinder and composing viewfinder into a single image, making operation significantly faster and simpler. Unlike most 35mm cameras, which have a swing-out door for film loading, the M3's film is loaded through the bottom via a removable baseplate, increasing structural rigidity.

As a result of the bayonet mount, lenses could be changed more quickly than with the old screw mount, and appropriate framelines would be set automatically depending on the lens in use. The M3 is notable for its .92x viewfinder, which offers significantly higher magnification than the current .72x standard on M cameras, as well as the .85x finder, which is highest magnification factor offered today. Early M3s had a double stroke film advance lever, while subsequent models were single stroke (often referred to as DS and SS, respectively). The double stroke lever was original implemented for fear of tearing the film during film advancement.

A drawback of the M3 is that it only features framelines for 50, 90, and 135mm framelines. Mounting a wide angle 35mm lens requires the use of a set of corresponding "goggles," which change viewfinder magnification accordingly. To date, the M3 is the bestselling M rangefinder, with over 220,000 units sold by 1966, when Leitz ceased production of the model. Despite its age and reputation, a used M3 can often be had for under $1,000 in today's market.

M2 (1957-1968)

Despite its lower model number, the M2 was released three years after the original M3. The M2 was intended to be a simpler, less expensive verion of the M3. Notable differences include the elimination of a windowed frame counter; the M2 instead had a disk encircling the advance lever, not unlike the earlier Leica III. The M2 introduced the lower magnification .72x viewfinder that has since been the standard on all M cameras. The benefit of this viewfinder was that the M2 could take wide angle 35mm lens without an adapter, thus it had framelines for 35, 50, and 90mm lens.

The bright-line illuminator window, previously made of ground glass on the M3, now consisted of a plastic Fresnel lens, ensuring more even and consistent lighting. The M2 went through a few minor variations through its life. A few of the early M2s lacked a self timer lever, although this is present on most units. Some models also have a button rewind in place of the typical lever.

Production numbers around 82,000 units. While both black and silver Leica Ms are common today, only around 2,400 M2s left the factory sporting black paint. Today, the M2 has a similar market price to the M3, and is valued for its durability.

M4 (1967-1975)

Ergonomically, the M4 set the standard for the M cameras of today. Instead of a vertically-oriented knob, there is now an angled crank for rewinding the film. The crank is attached via a universal joint and offers more leverage. This method is faster and more comfortable, but some purists prefer the original knob for its durability.

The film advance lever is now articulated with a plastic tip that sits flush with the body. Unlike the M3 and M2, the M4 eschews a removable film spool in favour of three take-up prongs in the camera, making film loading easier. Finally, the self timer and frameline preview levers are now metal-framed with plastic inserts, rather than the all-metal designs of previous Ms.

M4-2 (1977-1980)
As a result of poor M5 sales (see below), the M4 was reintroduced and later updated as the M4-2 in 1977. Production was moved to Canada to reduce costs, and the M4-2 also featured a hot shoe, and redesigned gears for motor drive capability. The self timer was also omitted.

M4-P (1981-1986)
The final iteration of the M4, the M4-P was released in 1981. The M4-P features 28mm and 75mm framelines and a Leica red dot logo near where the self timer had been on the original M4. Starting in 1984, the M4-P was sold alongside the M6, and production was moved back to Germany until it was finally discontinued in 1986.

M5 (1971-1975)

As of 2014, the M5 is the only Leica M to deviate from the classic design introduced with the M3. The M5 is notable for many reasons. For one, it was the first Leica rangefinder to feature TTL (through-the-lens) metering, eliminating the need for an external light meter. It was also the last Leica camera to be handmade entirely in Wetzlar (subsequent Ms have had their production outsourced to Canada, as in the case of M4-2 and M4-P, and Portugal, with final assembly in Solms).

Of course, the M5's most obvious claim to fame is its unusual, almost Frankensteinian appearance. The M5 is wide and taller than other Ms, and approximately 100 grams heavier. The rewind crank is now located in the bottom plate, rather than the top corner. The shutter speed dial surrounds the shutter release button, and protrudes over the edge of the top plate, allowing manipulation with a single finger. Interestingly, the M5 has its strap lugs on one side, allowing the camera to be hung vertically from the neck. Later version had a third lug, should the user wish to orient the camera traditionally. Due to its significantly different form factor, the M5 was unable to use existing accessories such as carrying cases, handgrips, and motor winders.

Unlike later Ms, the M5's exposure reading is displayed via a dual needle system through the viewfinder; when the needles are crossed, the image is perfectly lit. Subsequent metered Ms, starting with the M6, utilize LED arrows to indicate exposure. Additionally, while later Ms had off-the-film metering, the M5 had a CdS cell on an arm positioned between the lens and film plane, which moved out of the way as the shutter button was depressed. Due to presence of the metering arm, the M5 cannot be used with certain wide angle lenses and wide angle lenses, which protrude into the camera body.

Despite its technical and ergonomic advances, sales of the M5 were poor. It faced competition from more affordable Japanese SLRs, and ironically the Minolta-produced Leica CL. Production ended only four years after it was originally introduced, with figures standing at 33,900 units. Today, the M5 sells for around the same price as an M6 despite its relative rarity, perhaps due to it being a bit of an acquired taste. Silver chrome models are slightly rarer than the black chrome models due to lower production numbers. With the next numbered M, Leica returned to the proven formula used in the M3.

M6 (1984-1998)

After the commercial failure of the M5, Leica decided to return to the classic proportions of the original M3 with the new M6. Like the M5, the M6 featured a TTL light meter, but in a more elegant off-the-film form. Light coming in through the lens is reflected off a white dot on the shutter curtain into a silicon photodiode cell adjacent to the film plane. The light meter is activated by a half press of the shutter button, and can be turned off by turning the shutter speed dial to B (bulb). To produce a proper exposure reading, the M6 also has a film speed dial on the back, whose setting is transmitted to the camera via electrical contacts in the rear door.

Unlike its predecessors, the M6 utilized cheaper and lighter magnesium and zinc alloy top and bottom plates, rather than brass. Since the introduction of the M6 TTL, the original M6 has often been referred to be the retronym "M6 Classic." The M6 had more special editions than any other camera in history, ranging from the LHSA edition (101 units) to the Ein Stück Leica (996 units in honour of Leica Camera's IPO). Some of these special editions are now worth tens of thousands of dollars, and are quite popular among collectors in Hong Kong and Japan.

Starting with the M6, Leica M cameras have been produced in Portugal, with rangefinder calibration and final assembly completed in Germany. Due to the nature of German laws, Leica M cameras are still able to bear the statement "Made in Germany" in spire of this. Early M6s were engraved with "Ernst Leitz Wetzlar GmbH" on the top plate. However, in 1986, the Ernst Leitz company became Leica Camera AG, and was moved to the nearby town of Solms. The company would remain there until 2014, when it moved back to Wetzlar.

Beginning in 1998, the M6 was available with an optional .85x magnification viewfinder, which was closer in look to the original M3's. The M6 had the longest production run of any M camera, and was the second bestselling, after the original M3. Today, an M6 in good condition tends to go for around $1,000, with the M6 TTL selling for slightly more.

M6 TTL (1998-2002)
As its name suggests, the M6 TTL features through-the-lens metering. This is not to suggest that the original M6 did not have TTL light metering. What the M6 TTL brought to the table was TTL metering for flash. There is now a third LED in the viewfinder to indicate correct exposure.

The M6 TTL is distinguishable from its predecessor by its larger shutter speed dial, which has also been reversed. The dial now sports an additional "off" position and turns in the same direction indicated by the LED arrows in the viewfinder. This feature has been carried over to the M7 and digital Ms. The redesigned shutter speed dial also allows for easier turning with one finger while holding the camera. Other changes include a two millimetre taller top plate (to accomodate the electronics necessary for TTL flash capability) and a bare metal hot shoe (previously painted black on the black chrome M6).

M7 (2002-Present)

The M7 was the first M to feature an electronically fired shutter, which allows for aperture priority and intermediate shutter speeds. It is also the first M to support DX encoding, but film speed can still be set manually if the user chooses to do so. When using DX encoding, the user is also given the option of exposure compensation by rotating the dial on the back of the camera.

The drawback of the electronic shutter is that the the M7 requires batteries for normal operation. However, the shutter can be mechanically released in the case of battery failure for speeds of 1/60 and 1/125 seconds.

Starting with the M7, Leica returned to the use of heavier brass top and bottom plates that also allow for a black paint finish. To date, the M7 is the only film M with an electronic shutter, and a power switch along the shutter button axis. The M7 is one of two (the other being the MP) M cameras available for customization through the à la carte program, first rolled out in 2004. As of 2014, an uncustomized M7 sells for $4,995 new. As this camera is still in production, used examples are not cheap, but are still significantly less than retail.

MP (2003-Present)

While the 'M' in the original M3 stood for 'messsucher,' the name MP designation stands for "Mechanical Perfection." As such, the MP represents the ultimate incarnation of Leica's classic rangefinder formula. The MP combines the modern amenities of the M6 (TTL light meter, hot shoe, Fresnel lens bright-line illuminator window) with the build quality and ergonomics of the M3 (single-piece metal film advance lever, all-metal frameline preview lever, vertical rewind knob).

The MP is available with .58, .72, and .85x magnification viewfinders, and has been lauded for its return to the original M3 design with a condenser lens to reduce flare, a problem in some M6s. Along with the M7, the MP is one of two M cameras available for customization through the à la carte program. As of 2014, an uncustomized MP sells for $4,995 new.

M8 (2006-2009)

The M8 was the first digital Leica M, although it was not the first digital M-mount camera; that honor goes to the Epson R-D1, introduced in 2004. Unlike the R-D1, which used a 1.5x crop APS-C image sensor, the M8 had a 10.3 megapixel APS-H (1.33x crop) sensor supplied by Kodak. The M8 retains the on/off switch along the shutter button axis of the M7, and is also used to select drive mode (single, continuous, and self timer). In place of the film rewind is a circular monochrome LCD panel that displays the battery life. This feature is not present on any other M.

The M8 introduced a top shutter speed of 1/8000 seconds, two stops faster than the 1/1000 top speed of previous M cameras. The M8, as well as subsequent digital Ms, is approximately 14% thicker than film Ms to make room for the additional electronics and LCD panel. For the digital age, the M8 was also the first camera to feature an optical reader in the lens mount. This allows the camera to identify six-bit coded lenses and compensate for optical characteristics of individual lenses. All Leica lenses manufactured since the introduction of the M8 are six-bit coded. Older lenses could be sent to Leica and retroactively coded, although it appears this service is no longer offered. Third parties have since offered to code pre-M8 lenses, and one can also manually code their lenses temporarily with a marker.

Apart from the cropped image sensor, another drawback to the M8 was the lack of an infrared filter. As a result, blacks may appear purple on some photos. It is recommended that users install IR filters on their lenses, and Leica at one point offered free screw-on IR filters for M8 owners. Additionally, the M8 lacks an anti-aliasing filter, which is a double-edged sword; the camera is able to take advantage of the high resolving power of Leica lenses, but photos are more prone to moiré. Beginning in 2008, Leica offered an upgrade program for the M8, which included a sapphire LCD cover, more accurate framelines, and quieter shutter, at the cost of a maximum shutter speed of 1/4000 seconds. Due to the many perceived shortcomings of Leica's first foray into the digital rangefinder market, the M8 can now be had for very low prices, often showing up on eBay for under $2,000.

M8.2 (2008-2009)
Announced in September of 2008, the M8.2 included all the features of the M8 upgrade program, as well as replacing the black chrome color with black paint instead.

M9 (2009-2012)

The M9 featured a 35mm full frame Kodak CCD sensor with a resolution of 18.5 megapixels, allowing lenses to be used with their native field of view. However, it retained the same low-resolution 230,000 pixel LCD panel as its predecessor. Overall dimensions also remain unchanged. ISO tops out at 2500, but at the low range can be pushed to 80, compared to 160 on the M8. Since its discontinuation, the M9 continues to demand high resell prices (in the neighborhood of $4,000) as it is the only major option for a full frame M-mount digital camera apart from the new M240.

M9-P (2011-2012)
The M9-P was introduced in 2011, and sold alongside the M9. Differences between the two are largely cosmetic. The LCD cover is now made of sapphire, which offers greater scratch-resistance. The red dot logo and "M9" engraving have been omitted in favour of a "Leica" engraving on the top of the camera. The body covering, previously leatherette, is now vulcanite like that found on older M rangefinders.

M-E (2012-Present)

Positioned as a more affordable M model, the M-E is nearly identical to the M9. However, it lacks the frame-line preview lever and USB part. The M-E is instantly recognizable by its anthracite-gray top and bottom plates. It is currently sells for $5,450.

M Monochrom (2012-Present)

Based on the M9 chassis, the M Monochrom (commonly abbreviated MM) is the world's first full frame monochrome digital camera. As a result of the Monochrom's lack of a color filter array, Leica claims a 100 percent improvement in image sharpness over a color image sensor of identical specifications. The absence of a color filter array also means the sensor is more sensitive, allowing for a native ISO of 320. Maximum ISO is 10000. The Monochrom is identifiable by its all-black chassis. It currently sells for $7,950.

M (M240) (2012-Present)

Sometimes referred to as the M240 (in reference to its 24 megapixel resolution) to differentiate it from previous Ms, the M is the first Leica rangefinder with a CMOS sensor. This time around, Leica has collaborated with the Belgian CMOSIS, rather than Kodak, which supplied the sensors found in the M8 and M9. The M240 is the first M to feature video recording and Live View. Notably, the bright-line illuminator window has been omitted, with the framelines now illuminated by LEDs, a feature carried over from the Leica M9 Titanium.

Thanks to its Live View capability, the M240 can accept Leica R-mount lenses via an adapter. In Live View mode, focus peaking is available on the M's 920,000 pixel LCD panel. In addition to the rear LCD, the M can mount an external EVF (electronic viewfinder) on its hotshoe. Video recording is activated via a button to the right of the shutter button, and resolution tops out at 1080p.

On the back, the directional arrows have been replaced by a directional pad; and the scroll wheel, which surrounded the arrow buttons on the M8 and M9, has been moved to the top right corner, also serving as a thumb rest. At release, the M240 proved to be exceedingly popular, with backorders of several months. As of 2014, the M240 sells for $6,950.

M-A (2014-Present)
Announced for the 100th anniversary of Leica, the M-A is a fully mechanical rangefinder camera with no light meter. It appears to be based on the MP. As of now, the M-A is only available as part of a limited edition set which also includes an M Monochrom and three Summilux lenses (28, 35, and 50mm focal lengths). The Edition 100 set is limited to 101 units. Both cameras in the set are made of solid stainless steel. It is not yet known if Leica will produce the M-A separately as a standard option in its lineup in the future.

Other
Less significant Leica M cameras include the M1, which was released in 1959 after the M2. It lacked a rangefinder and only had viewfinder framelines for 35 and 50mm focal lengths. Successors to the M1 were the MD, MDa, and MD-2. These lacked any sort of viewfinder for image composition, and were intended for scientific and institutional use through the attachment of microscopes or the Visoflex, which would effectively transform the M into an SLR.

Not an M, but the Leica CL is noteworthy for being an M-mount camera. This was a joint venture in 1973 between Leitz and Minolta. The CL was a compact rangefinder camera manufactured in Japan by Minolta, with two M-mount lenses made especially for it by Leitz in Germany. One of these lenses was the 40mm Summicron-C. While Leica's official position was that the 40mm would not work properly on other M-mount cameras, it does with the exception that there are no 40mm framelines on Leica Ms. By default the lens will bring up 50mm framelines, but the mount can be modified to trigger the 35mm framelines, which more closely represent the image projected by the lens. Sold alongside the M5, its low price and compact footprint had the unintended consequence of cannibalizing sales of its bigger brother. As such, the CL was discontinued in 1976.

Notes
All images in this article are used under the Wikimedia Creative Commons license, unless otherwise specified. I do not claim to be the author of said images, and do not purport to have the endorsement of the original authors. Authors are credited for their respective works. For photo sources and Creative Commons Attribution licenses and terms, click on individual images.

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A Brief History of the Leica M