Leica Screw Mount - LTM Rangefinder Cameras
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- Leica Screw Mount Cameras - the 1930's through the 1950's -

- This page was written by Andrew Yue. All images and text are the copyrighted. -

Leica is a name that is synonymous with the birth of 35mm photography.   Although Leica has in the past made a wide variety of optical products - such as binoculars and microscopes - the name is also synomymous with rangefinder cameras.   In truth, the success of 35mm film in becoming a serious photographic format was in a large part courtesy of a not so large German microscope firm, E. Leitz of Wetzlar, the parent company of Leica.

The original Leica screw mount was the creation of Oskar Barnack - who was the lead Leitz designer responsible for its development.   Work began on a prototype camera as early as 1914 and subsequent development would take another decade.   The first Leica camera, the Model A, was publically introduce in 1925.

- The Leica I and the Leica II -

- A Leica I fitted with a separately purchased rangefinder. -

Oscar Barnack's ultimate goal was to offer a small precision camera that could be carried anywhere.   The Model A featured a cloth focal plane shutter.   While not the first to use 35mm motion picture film in a still camera, Barnack's innovation was that he turned the camera sideways, then widened the image frame from a standard 18mm by 24mm of the cine format to the 24mm by 36mm frame that we now know as the 35mm film format.

In 1930 a Model C was introduced,(* shown above with a separately purchased rangefinder. *)   The Model C, which is normally referred to today as a Leica I, - featured a 39mm Leica thread mount - to allow for removal of the lens.   In 1931 Leitz standardized the distance between the outer base of the lens mount to the film plane at the rear of the camera to 28.8mm.

In essence, the first 35mm system camera was born.   After 1931, the Leica I could accept any Leica LTM lens.   The Leica I / Model C - was the third variant of Barnack's original 1925 design and the basic building block for the next camera, the Leica II - which early users referred to as a Model D.

To review - the Leica screw mount is also called the Leica thread mount or LTM for short.   Standardized LTM lenses use:

  • An 39 mm by 26 tpi screw mount, tpi = # of threads per inch.
  • 28.8mm distance between the lens mount and the film plane

- A Leica II in use. -

The Leica II of 1932 introduced a built-in rangefinder focusing apparatus that coupled to a removeable LTM lens.   Lenses now featured a focusing cam that protrude from their base to interact with rangefinder mechanism built into the camera.   It's rangefinder apparatus allowed the photographer to focus the Leica II without any guess work.

The raised top cover for the viewfinder and rangefinder optics of the Leica II are what easily distinguishes it fromm a Leica I.

The architecture and shape of the Leica II came to represent the essense of 35mm rangefinder photography for more than 20 years.   Form follows function on a Leica screw mount camera of this iconic design.   The viewfinder and rangefinder apparatus utilize separate eyepieces - one for the rangefinder apparatus, which is magnified - and - a second optic that is centered between the two RF windows, which is used to compose the photograph.

Coincidentally, Zeiss Ikon introduced their first Contax in 1932.   Although both were introduced in the same year, they are very different cameras.   The Contax resembles a streamlined brick.   The Leica II on the other hand - has a design firmly rooted in age of steam engines.

To say Oskar Barnack's rendition of the Leica II was an iconic design is almost an understatement.   Even Leica's all-new IIIc in 1940 didn't tamper with basic architecure or shape of the original Leica II.   By the 1950'ies - more than one Japanese camera maker would also slavishly copy the design after the German patents became null and void at the end of Worlda War II.

The Leica II shown above is spartan by modern standards, but it is ever capable of precision photography, albeit with seven very old-fashioned shutter speeds to choose from.   Basically built on a modified Leica I body - the Leica II set the mold on what was to become the Leica III.

- The Leica III series -

Introduced in 1933, the Leica III was Leitz's response to the introduction of the Zeiss-Ikon Contax.   It was also Oskar Barnack's last design before he died in 1935.   Unlike the Leica II, the Leica III includes an extended range of slow shutter speeds.   The added slow speeds range from 1/20th of second to one full second.

Underneath the top cover - both the Leica II and III share the basic body shell of the Leica I.   To produce this third variant, a separate front mounted dial was installed onto the front body shell of the Leica camera.   The Leica III camera uses the same RF/VF architecture as the Leica II.   Both the Leica II and III are fitted with a 1.5 magnifier to their rangefinder optics - but the III gets an adjustable diopter.

An additional feature not found on the Leica II, the Leica III also has two lugs or eyelets added to the body for a camera strap.

Aside from the extra front mounted shutter speed dial and the two lugs for a camera strap, the Leica III looks almost identical Leica II.   As a tribute Oskar Barnack's frugal genius, one body shell now served as the basic platform for the Leica I, II, and III.   E. Leitz could now sell 35mm cameras at three different price levels.   Any Leitz LTM lens with a focus cam could seamlessly couple with a sensor tab within the camera body of the RF apparatus built-in to both the Leica II and III.

The front dial is only used to set the added slow shutter speed escapement.   The top shutter speed dial was still used in the same manner as the Leica II to set speeds faster than 1/20th of a second.   With the Leica III, the photographer could select shutter speeds between 1/500th of a second to 1 full second - versus the Leica II - which only ranged from 1/500th to 1/20th of a second.

The Leica III received two updates:

  • A Leica IIIa was released in 1935 and it added a top speed of 1/1000th of a second.
  • A Leica IIIb was released in 1938 with a redesigned viewfinder optic, which brings the RF and VF eye pieces close together.

While it was an improvement over the Leica II, the Leica III still did not match its major competitor, which was the better specified Zeiss Ikon Contax.

Fortunately for Leitz, the relatively uncomplicated horizontally moving, twin curtain, cloth focal plane shutter, that been designed with the Leica I in mind, proved to be very reliable even when extented to the Leica III.   On paper at least, the newly released Contax was a very impressive design, but its magnificent all-metal, roller blind shutter proved to be troublesome during its early years.

In 1938 those early Contax troubles would disappear with the introduction of the Contax II and III.   Both cameras were superb.   The shutter issues were resolved.   Plus, Zeiss fitted the new, improved Contax a 90mm base-length between the RF optics and a combined RF/VF window.   The Contax III is a rather massive affair, because it features a built-in light meter.   Zeiss Contax would have remained on top - if the Second World War had not occurred.

- The Leica IIIc and the later Barnack inspired Leicas - -

The Leica IIIc was introduced in 1940 with a total redesign of the body and shutter crate   The IIIc is not only a bit larger than it predecessors, but features an all new single cast top cover.   Remarkably, the external appearance of the early Leica IIIc is almost identical to the previous III, IIIa and IIIb cameras of the 1930's.

The IIIc was a mainstay of Leica's line-up through out the 1940's.   The original 1940 design would see some minor modifications over the next decade until the debut of IIIf of 1950 - which would include the addition of built-in a PC flash terminal and an adjustable synchronization system for various types of flash units that were in use.

The IIIf would be essentially an update IIIc.   To prove the point, the above photo shows a late Leica IIIc that was modified post-1950 to IIIf specifications - to include an adjustable flash synchronization dial mounted below the shutter speed dial.   A gussied up film advance knob has been added from the IIIf parts bin.   To complete the modification, the Leica technician screwed a thin metal plate with the necessary engraved synch numbers to the top cover of the older IIIc.

The war years took its toll on Leitz.   For most of the late 1940'ies, the IIIc wasn't as well finished as the late 1930's IIIb.   Cut off from the Far East, Leitz no longer had access to the same high-quality silk curtains that graced the pre-war Leicas.   Chrome was a strategic material in short supply, so by the end of the war, most Leicas had painted bottom plates and top covers. &nbps; At this time substitute shark-skin like material was often use in place of hard rubber vulcanite covering on the lower body.   The chrome plating on the post war IIIc has tendency to pit or peel as well.   They also no longer have a stepped platform for the rewind release lever of the early IIIc.

By 1949 most of these cosmetic issues had been corrected, but if buying a post war IIIc - do have the shutter curtains checked and do expect to have to replace the replacement beam splitter for the rangefinder.

Even though all was not perfect in Leicadom during the war and immediate post-war period, the IIIc is a brilliantly designed camera.   It endured under difficult conditions.   Collectors shun the post-war IIIc - which again no longer has a stepped platform for the rewind release lever - nor - the tiny knob for the diopter on the RF eye piece.   A post war IIIc is still a wonderful user camera - because it is affordable and it retains the then recently introduce miniature bearings to the top spindle of the rotating shutter drum.   This was originally a wartime modification to improve reliabilty in extreme cold weather that became a standard feature on all future Leica III series cameras.

- The Leica IIIf, Black Dial versus Red Dial -

To easily tell a Leica IIIf from an unmodified IIIc, just look for the flash synch dial, which will not be found on an unmodified IIIc.

On the first IIIf of 1950, the engraved contact numbers below synchronization dial are painted black.   Hence, the early IIIf is referred to as a IIIf BD - which refers to the black dial.

The adjustable synch dial allowed the photographer to delay the opening of the shutter to coincide with the peak brightness of the flash.   Magnesium filament bulbs take a good bit of time to ignite and reach their peak brightness.

Not all single use flash bulbs were created equal.   M-type flash bulbs burned brightest about 18 to 22 milliseconds after their intial firing.   That's 1/50th of second delay.   F-type bulbs only needed about 5 milliseconds to reach their peak brightness, which is about 1/200th of second.   Magnesium fliament bulbs burn for a longer duration than a modern strobe and for an even longer flash duration their was the FP-flash bulb.   FP bulbs also took 5 milliseconds to ignite, but burned long enough to use a shutter speed up to 1/1000th of second - which on a Leica meant this type of bulb had to burn at peak brightness for about 1/4 to 1/3 of a second.   By contrast the duration of a modern electronic flash is about 1/1000th of second.

- Flash Table for a Leica IIIf RD. -

With regards to the added flash synchronization system of the IIIf - this was a big deal back in the early 1950's when Kodachrome color film was rated at a sluggish 12 ASA.   25 ASA to 50 ASA was the normal B/W film rating.  

So, with the above film speeds, the use of a flash was essential for hand-held indoor photography.   Since both the duration and the delay of magnesium filament bulbs varied widely, the Germans over-engineered the flash system on the Leica IIIf.   Today's photographers will only be using an electronic flash unit, if they feel the need to try flash photography with an old Barnack.

Synchronization Dial Settings for a modern electronic flash:

  • IIIf BD - Synch dial set to "2" - Shutter speed set to 1/30th or slower
  • IIIf RD - Synch dial set to "0" - Shutter speed set to 1/25th or slower
  • IIIf RD - Synch dial set to "20" - Shutter speed set to 1/50th of second

In 1953 - yet another redesign of the shutter assembly led to the IIIf Red Dial.   The IIIf RD had an improved flash synch speed of 1/50th of second versus the 1/30th of a second of the IIIf BD -when using a modern electronic flash.   The late IIIf also seems to have returned to higher quality shutter curtains, along with a more durable chrome plating to the exterior and features a beam RF splitter that seems to age much better than than the earlier IIIf BD.

In 1954 Leitz added a self-timer to delay the shutter release - so the photographer could get in the photo.

Other improvements included on both versions of the IIIf are film speed reminder at the top of the winder and a tab on the removeable base plate to prevent modern preloaded film cassettes from slipping downward during use.   The Leica IIIc lacked this tab on its bottom plate.   Without the protruding tab, modern preloaded film may ride so low across the film gate that the exposure occurs over the sprocket holes at the bottom of each frame.

- The Leica IIIf versus the IIIc -

Unlike the Leica IIIc both versions of the IIIf will accept modern preloaded film cassettes without any of the off center framing issues that results in sprocket holes appearing in the image.   The IIIf Red Dial tends to age better than either the IIIc or IIIf BD with regards to the brighness/clarity of the RF patch and features what seems to be better quality shutter curtains.

For the purist, the Leica IIIc is still the simpler design.   It has all the bare essentials for ambient light photography.   Chances are the camera will need to be fully serviced by a camera technician - which may or may not include a new set of shutter curtains and the installation of a new half-silvered beam splitter to bring back the RF to its origninal specs.

- The Leica IIIg -

Leitz released the Leica IIIg in 1957.   It was the final variant of the IIIc architecture.   A newly designed top cover with a larger and improved viewfinder are immediately noticeable.   Also notice the extra rectangular, frosted window for the projection of two different frame lines into viewfinder.

Had the Leica IIIg been released in 1950 or 1953, it would be far more numerous today.   The truth is that Leitz had shifted the playing field with the 1954 release of the Leica M3.   The new Leica M models were an all new design with a new lens mount and an improved camera body that nothing in commonality to the IIIc derived IIIf or IIIg for that matter.   The Leica M3 set a new benchmark for 35mm rangefinders that would last nearly 50 years.   Leitz at long last had a camera that outclassed both on paper and in operation its main German competitor, the Contax.   Canon and less so Nikon would totally revamped their 35mm rangefinder cameras by 1957.   Zeis Ikon on the other hand seemed to have interest in their high-end rangefinder cameras, allowed their Contax cameras wither on the vine.

The new larger viewfinder of the IIIg with two sets of illuminated framelines housed in a larger top cover was inspired by the even larger Leica M3 viewfinder - which had of course had three sets of illuminated framelines.   The M3 was the show stealer.

The IIIg was in commercial production for only 3 years.   Japanese manufacturers were by now ramping up production of cameras which incorporated some of the ergonomic improvements of the Leica M3 and were adding a few of their own.   The IIIg not only had to compete against the better spec'd Canon P and Nikon S3, but after 1958, the newly release Leica M2.   The Leica M2, a sister to the M3, was to be a runaway success.

The biggest failing of the Leica IIIg against the competition is it still lacked the combined VF/RF assemblies of its competitors.   A combined viewfinder and rangefinder assembly allows for a single, much larger eye piece for focusing and composing at the same time.

While not the most stylish camera at the end of 1950's, the Leica IIIg features the following changes when compared to the IIIf Red Dial.

  • A larger .7 mag viewfinder with two sets of illuminated, parallax corrected, framelines for the 50/90 focal lengths.
  • Both shutter speed dials are calibrated with a modern shutter speed progression - which we still use today.
  • The front shutter dial for the slow speeds is now a one way progression versus the old two way progression.
  • Separate flash synch dial was deleted to be replaced with two flash settings at 1/50 and 1/25th of a second on the shutter speed dial.
  • The film reminder dial is now located on the back of the body shell and exceeds ASA 100.

The IIIg - with its taller and more modern viewfinder housing - loses a certain "je ne sais quoi" of the earlier Barnack cameras.   In use the updated viewfinder is a joy to compose with when compared with the older Leicas.   The viewfinder's parallax corrected frame lines move as the focus is adjusted.

As alluded to above, at the end of the 1950'ies the photography world was moving on to more modern designs, not only from the competition from Japan, but also from the newly introduced Leica M3.   Consequently, the IIIg is not as common on the used market as either the older IIIc or IIIf.   It makes this camera attractive to collectors.   A IIIg in good condition will sell for double or triple the price of well cared for IIIc or IIIf.

- Using a Barnack size camera today -

The main thing missing from photography in the modern digital age is the print.   With a Leica screw mount or any other legacy film camera for that matter - one has to judge their photographic results on a piece of paper.   The choice of lenses and equipment are secondary concerns, but they do affect the final print.

Leicas and their lenses keep their value.   A well made entry-level digital SLR with a with a moderately priced zoom as opposed to rock bottom entry-level lens can be purchased for the same money as a IIIf with three lenses.   The DSLR body on the will probably be worth virtually next to nothing on the second-hand market in a decade's time.     A Leica IIIc or IIIf will probably be worth what you paid for it in 10 years, maybe more.

Unfortunately, through the lens metering, histograms, auto focus, auto exposure, macro and long distance telephoto are not part of a Barnack Leica's reportoire.   For color photography, the digital SLR is by far the most practical choice.

So, one may ask, so why use an old Leica screw mount camera?

Aside from the handling a pocketable, compact camera that is very well built, one is totally free of photography by wire experience that in today's norm.   With a collapsible lens or svelte wide angle mounted to the camera, a Barnack fits in a coat pocket, just like it did in 80 years ago.   Its native resolution is at least equal to that of a 12 megapixel full-frame digital SLR - although most DSLR cameras now surpass the 12 megapixel threshold.

The word photography literally means to write with light.   B/W imagery has only the nuances of gray tones, shapes and subject matter / context to work with.   It is becoming an uncommon medium today, and to be done well B/W requires a more sophisticated technique with regards to composition than with color photography.   For me, an old Barnack and its vintage lenses are a perfect fit for black and white photography.

For an old-school traditionalist good B/W photgraphy reveals itself on the print rather than on a computer monitor.   If nothing else, B/W prints from negatives exposed with a vintage Leica III series and their old-school optics delivers a look that is unique in today's digital landscape.   Digital raw files converted to B/W are gaining popularity, but have a different tonal signature and requires a more controlled lighting due to digitals more limited exposure latitude.   The Bayern pixel pattern renders a much different signature than that of traditional silver halide B/W films, such as Tri-X or APX 100.

Unfortunately, most amateur photographers still think the B/W photography is the purview of professionals.   In reality, B/W film is easier to develop at home than you would think and D.I.Y development doesn't require a darkroom.   Only the next process - the traditional printing onto light sensitive B/W photographic paper requires a darkroom.

With regards to a darkroom - my set up fits in a walk-in closet that is adjacent to a bathroom. - It is free of computer hardware or software upgrades. - In essense, I have had the priviledge to use the same printer for a dozen years, with no needed upgrades and I'm probably the third owner of this set-up.

While the diminutive Leica screw mount may not a clear winner in the multipurpose photographic world we live in today, it is still a powerful photographic tool.   It captures its images without pull down menus, numerous electronic buttons or battery power of any kind.

As a primary camera system that does everything, a screw mount Leica is not best choice, but for intimimate, close-in shooting of scenes of people or places - an old Barnack more than earn its keep.

If you want to get the more from film, check out my take on medium format folders on the link below.

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- Revised on September 26th, 2018 -