Welcome to my M-1 information page. This page is a documentary about the Olympus M-1, what it is, and what makes it so special in the Olympus OM lineup. Much of the information being presented here has been gathered as part of my M-1 restoration project.

The M-1 and M-SYSTEM components were introduced by Olympus in 1971 and produced until February 1973. The system consisted of a single body, the M-1, and a collection of lenses and accessories. It is known that the following lenses were available and actually sold as M-SYSTEM lenses: 28mm f3.5, 35mm f2.8, 50mm f1.4, 50mm f1.8, 55mm f1.2, 135mm f3.5, 100mm f2.8, 200mm f4.0, 75-150mm f4.0. In addition, the following accessories were also produced and sold as M-SYSTEM components: VST-1, Auto Bellows, and Varimagni Finder. The name M-1 and the M-SYSTEM designation was changed to OM-1 and OM-System due to a complaint from Leitz. Since 1959, Leitz had been using the M1 designation for its rangefinder camera and felt Olympus was infringing on a trademarked name. Olympus honoured Leitz's complaint and agreed to change the name. Unfortunately, by the time that decision was made, quite a number of M-1's and M-SYSTEM components had already been built and sold in the marketplace.

Since the M-1 was the first OM model to be produced, it contained a number of unique features which were either changed or completely dropped in later OM-1 production runs. These features can be used to identify an M-1 and to roughly estimate when an M-1 was produced. The information presented here has been gathered from disassembly of an M-1 and from discussions with former Olympus technicians.

There are a number of externally visible difference between an M-1 and a late-model OM-1. The most evident difference is the inability to accept a motor drive or winder. This can be seen by examining the bottom plate of the camera and looking for the missing MD cover plate. The only cover plate which should be present on an M-1 is the battery cover.

The M-1 also used a different back than later vintage OM-1's. The back can be identified by the smaller film pressure plate, closer spaced film pressure plate mounting studs, and the early style film canister retaining assembly. The M-1 pressure plate measured 51.5mm x 38mm whereas later vintage OM-1's used a larger 60.5mm x 38.5mm sized plate. To measure the spacing of the film pressure plate mounts, it is necessary to remove the film pressure plate. Once the plate is removed, the spacing between the two studs can easily be measured. The spacing on an M-1 back should be 45mm centre to centre, compared to the later 52mm spacing. With the back open, the film canister retaining assembly is easily visible and is shown in the accompanying photo. The retaining assembly was redesigned such that two "fingers" applied pressure to the film canister to hold it in place.

With the film pressure plate removed, it is very easy to identify the production date of the camera (as long as the back has not be switched from another body!). On the back of the film pressure plate you will find a production stamp located in the centre of the plate. It would look similar to the attached photograph. The first character (the Japanese symbol) represents the manufacturing plant which built the camera. The next two digits are a date code which represents the year and month in which the camera was built. In this particular case, the code "31" indicates this particular M-1 was manufactured in January, 1973. It is believed that this was the last production run of M-1's. Very early OM-1's contain a production date code of "32" which is February, 1973.

The M-1 also used a slightly different style door latch mechanism than what was used on later OM-1's. The M-1 mechanism used a flat style hook instead of the more common "bump" style. You'll notice in the attached photograph that the latch hook is completely flush with the body casting. Later variations of the latch raised the hook away from the body casting.

One final external difference exists between an M-1 and later vintage OM-1's, the M-1 used slotted style screws on the lens mount. In later OM-1 production runs, the slotted screws were dropped in favour of phillips (star) style screws.

The most significant difference between an M-1 and the newest OM-1's lies in a number of internal changes that were made. There were dozens of changes made, some were design improvements, some addressed problems with the original design, while others merely improved the manufacturing ability of the OM-1. Presented here are only those changes which were made shortly after the M-1 production terminated.

Under the top cover of the M-1, there are a number of clearly visible items which were changed early on in the OM-1 production cycle. The above picture points out several of these items which will be discussed further.

Meter Resistor R4

The original M-1 meter circuit consisted of four resistors labelled R1 through R4. Resistors R1 through R3 are used to adjust the meter for mid, high and low light levels respectively. Resistor R4 was present in the circuit to allow the meter to be calibrated to within 1/16'th of a stop. All M-1's left the factory with resistor R4 present and calibrated. Early on in the OM-1 production, it was determined that resistor R4 added very little value to the final accuracy of the exposure meter, so it was decided that resistor R4 would be dropped from the circuit. However, the circuit board remained the same, only the resistor was dropped.

Meter Needle Deflector

All M-1's were built with a meter limit warning circuit surrounding the galvanometer (ie. the meter) which would fully deflect the meter needle whenever the meter hit its low-light limit. The sudden deflection of the meter needle was meant as a warning to the photographer that the meter had hit its low-light metering limits. Although the circuit worked, it proved troublesome in the field and occassionally caused the meter to be permanently deflected. The disadvantages far outweighed what little benefit it provided, and the circuit was dropped early on in the OM-1 production.

Red-Black-Green Wiring

The photocells used in the M-1 metering circuit are also different from the ones used in later vintage OM-1's. The newer photocells had better resistance characteristics which made it easier to calibrate the meter. All M-1's used the original type of photocell, which can be identified by the red-black-green colour wires coming from the photocell. Newer photocells used the red-black-pink colour scheme.

Missing Motor Drive Facilities

As we already know, all M-1's were originally produced without the ability to accept a motor drive or winder. More evidence of this can be found by examining the first (primary) wind gear. The first wind gear (the one on the left) is missing the spring loaded ejector pin which is found in the centre of an MD capable first wind gear. The M-1's first wind gear should have a slotted screw present in the centre of the gear. In addition, the location where the motor drive electrical contacts are attached will be slightly different depending on the vintage of the M-1. The more recent M-1's will have the mounting holes for the MD electrical contact pre-drilled, tapped and filled with a screw. The earliest M-1's have no mounting holes present. Here is a photo of what a late-model M-1 would look like. The two slotted screws are used to secure the MD electrical contact bracket to the body.

German

English1

English2

Instruction Manual (Japanese)

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      (1) Thanks to John Foster, (2) Thanks to Lars Petersen

All the M-system bodies and lenses were produced at the Olympus manufacturing plant located in Suwa, Japan. M-System items were sold across the world, but the majority of the items seem to have been originally sold in Asia (Japan and Hong Kong) and Europe (Germany). Over time the items have migrated across the world and today they can be found virtually anywhere. The M-System items were produced in varying quantities depending on the popularity and price of the item. For example, the 50mm f1.8 was produced in far larger numbers than the 55mm f1.2. By tracking the serial numbers of M-System items and comparing those serial numbers to early OM-System items, we can make an educated guess as to the approximate number of M-system pieces produced for each item. For the M-1 body we have the added advantage that we can also track the production date of each body and correlate the production sequence with the serial number. After collecting data for a number of years, we can now summarise the production data as follows:

The "rarity" score is graded on the following scale "Common - Less Common - Rare - Very Rare" and represents the probability of locating that item when searching for M-System items. Keep in mind that all M-system items are far less common than OM-System items, but some M-System items are particularly difficult to find. A grading of "Common" does not imply that the item is easily located, it just signifies that the item is easier to locate than a "Very Rare" item.

For each item a grade is given for the amount of confidence we have in the production number estimate. The scale used to measure the confidence is "Very High - High - Good - Low - Very Low" and represents the likelihood that the estimated production number is accurate. The grade is based on how much actual data has been collected and how close the largest M-System serial number is to the smallest OM-System serial number. The closer the two serial numbers are the more likely it is that we have a complete representation of the M-System data.

From the data collected we can also see that the M-1 body serial numbers were not assigned in strict sequential order. Although the serial numbers were mostly assigned in an increasing order, there were small batches of serial numbers which were assigned out of order. If we ignore those out of order batches we can see that Olympus was producing approximately 2,000 M-1 bodies per month in early 1972 with production ramping up to approximately 5,000 M-1 bodies per month by early 1973. The production figures match very closely with the estimate of approximately 52,000 M-1 bodies.

The table below provides the raw data used to compile the above summary.

The following table lists all the known components of the M-System along with their serial number and production date (if available). The data in this table will be expanded as new information is discovered.

 
Early OM-SYSTEM Items

Many thanks go to Clint Rumbo from Photosphere and John Hermansen from Camtech for answering my numerous (and sometimes nagging :-) questions regarding the M-1.

All photographs for this web page were taken using Olympus OM equipment (80mm macro, 135mm macro, T-8, T-10).