Modern Classic SLRs Series :
Olympus OM-1 (n) - Part 3

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Well, that is not my main concern as far as OM-1(n) relates. The biggest headache for any OM-1(n) user is probably thinking how to get a proper battery(ies) or substitute for the camera's metering circuit. The OM-1(n) uses a obsolete mercury cell to power its metering. The proper cells to use is 1.35 volt mercury battery MR9 (Eveready or UCAR EPX625, Mallory PX625, or equivalent). Many countries have ban these environmental hazardous old cells and making them very hard to locate. The OM-2(n) introduced later, uses two easily accessible 1.5V silver oxide batteries and don't present such problems. Anyway, the battery issue could explained why OM-1(n) is not highly recommended as a good start up SLR camera for beginners even if the price isso much cheaper in comparison as reflected in the used market. However, even with this problem, this little jewel mechanical camera has always been a hot favorite among many collectors and moreover, it is the only Olympus SLR that still offers a mirror lockup feature.

Tips: Based on the Olympus FAQ maintained by Hawkins & Co... It mentioned there is a company produces an adapter that not only drops the voltage of a silver oxide battery to 1.35V which is similar to Mercury Cell, it also adapts it to fit mechanically in a battery well the size of a PX625 mercury cell (The normal Silver oxide and alkaline cells have different voltage and physical size). It retails at $29.95 plus $1.50 shipping from C.R.I.S. Camera Services 800-216-7579, 602-940-1103 (outside US). Some OM users claimed it works as advertised and is likely a cheaper long term alternative than Wein lead-air button cells, which constantly leak current from the moment they are exposed to air.

Exposure compensation When the needle is centered, the camera controls are set for correct exposure of a subject with a normal distribution of tones, i.e. averaging out to a mid-tone. If the subject has an unusual distribution of tones, you need to give less or more exposure than the meter indicates. If you are still confused or new to master this well, go to as dedicated section addressing Fundamental of photography & Basic of handling a mechanical SLR camera.

Shutter Mechanism One of the weaker link in the OM-1 series models (Or for that matter, apply to many other OM models), where most of the time, rivaling makers like to highlight is its shutter. Other than the Cosina made OM2000, the focal plane type shutter for most OM SLR cameras are still made of rubberized silk fabric. The choice of materials would make one always associate it with a some potential problems such as reliability under hard professional use, resistance to heat and humidity.

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But around the shutter mechanism, it has many original ideas from Olympus, materials such as nylon strings are used instead of the more common tapes or ribbon as a space saving device. (Actually, there were rumors that it was a type of thread used in medical or surgical applications, an inspirational idea from Mr. Maitani (Its Chief Designer) during a short stay at the hospital when involved in an accident, adoption of such idea enabled the height of the pentaprism of the viewfinder section to lower further into the camera body and thus made the camera possible to be smaller and more compact in size.

OM1's shutter is a horizontally traveled focal plane shutter type with ring mounted controlling speeds from 1 to 1 /1000 second plus B. Most would think one of the weaker points found in an OM SLRs is around its shutter unit. Not in terms of accuracy or performance, but rather in its material used. All OM-1, OM2, OM3 and OM4 series models are still using specially treated fabric as the base material for its shutter curtain. I would not like to associate it with reliability issues but Olympus seemed undisturbed by users' concern all these years on this particular issue.
Well, the shutter curtain has the cloth on the side facing the film surface. The inspection standard would required that any position in the picture frame, the amount of overlapping of curtain edge (Metal) should be over 2.5mm. When the shutter is wide open at a slow shutter speed, the second curtain should not be appear in the picture frame.

<<--- A back view of an OM1MD. When you are trying to acquire such a camera in used condition, it is always a good practice to open the film back first and do a visual inspection. First thing of cause is the shutter curtain See if there is any deformation, fungus filled or loosening of the cloth curtain

But despite this, users' confidence towards Olympus products is high, but whenever a new SLR model is being introduced, Olympus has a lot to emphasize on the improvement made within the shutter design (For an example, Olympus claimed the shutter in the OM4 has 50 improvements made over the original design first used in OM2(n) but there is literally little to mention on the material used.)

But many of those OM-1(n) and OM2(n) models survived over the last 2-1/2 decades and little problems arising from shutter curtain, so that should not be too much of a concern for you and I.

The complete operational sequence of the horizontal traveled shutter mechanism of OM-1 camera. The timing chart illustrated at left is based on curtain movement from one edge to another of the mask.

It does not include the movement of the first and second curtains before they appear one end of the mask and after they will have reached the other end of the mask. Related: Understand how a Focal Plane Shutter Works.

The OM-1(n) model has a normal range of speeds from 1-1/1000 sec, plus a B setting. The slower shutter speed is color coded so as to provide a visual aid to differentiate it from speeds of higher scales. It also has both 'X 'and 'FP' synchronization settings, it can be changed by a switch around the coaxial socket.

You can make use of the socket for off camera multiple flash setup or use it with older flash with only sync cable. If you still persistently used flash bulbs which I doubt many still do, you may make use of the table below for a rough reference guide.


Flash Lamp

Shutter Speeds

Time lag: X-Contact: at 1/60 sec, it should be switch in within 1.5ms of the closing action of the second curtain, upon completion of the first curtain opening. FP-Contact: It should be switched in at 8-14ms prior to commencement of the first curtain action.


























Electronic Flash
























M : FP












To Operate: Turn the red dot to "FP" for use with FP type bulbs and to "X" with electronic flash, M or MF type bulbs. With FP type bulbs any shutter speed up to 1/1000 sec. can be set, and with electronic flash the shutter can be set up to 1/60 sec. Note: But the later OM-1N bodies has improved when used with Shoe 4, it will auto-sync in X, regardless of the position of the FP/X switch.

A quick view of the FP/X Switch and Flash Synchronization Circuit

n a single reflex, normally it takes the mechanism wherein the > Contact is always kept "ON" and/or it is switched on again when the film is advanced. This causes an explosion at the time of the film advance. Therefore, normally the X-Contact piece is made movable to prevent it. However, because it means unstable positioning of the contact piece, FP and X are connected parallel in case of the OM-1.

The FP contact has to be switched in within 10 ms. prior to complete opening of the first curtain. Thus, normally, the signal is received from the mirror driving mechanism. In case of THE OM-1, the signal notifying the mirror rising is transmitted to the shutter which in turn makes the switch works. X-Contact: Since the X contact is to be switched IN immediately upon completion of the first curtain opening, the switching action is carried out by the first curtain cam and the first curtain brake.

Another highly unusual feature found in early OM bodies is at the top of pentaprism. There is a accessory socket where it accepts different types of clip on accessory shoe, Olympus can claimed it as an "cableless contact" feature but it is just an accessory that can be screwed into the tiny opened socket. Frankly, I find there is no apparent reasons of why OM SLRs designed with a removable accessory shoe and I think Olympus find it hardly convincing as well and eventually since OM-10, all OM bodies was incorporate a fixed accessory shoe.

Relative: Olympus Flash Group (4 Parts) Quick Reference Guide: Olympus T45, T32, T20, F280, S20, T10 Ring, T8 Ring, T28 Macro Single, T28 Macro Twin, TTL Quick AUTO 310, Quick AUTO 300, PS200, PS200 Quick and T Power Control Version 1

Nevertheless, you still have to understand nature of how it works in its compatibility between camera Models/Shoes. i.e. Older M-1 and OM-1's can only accept a Shoe Type 1. OM1(n) and OM2n should use a shoe Type 4; original OM-2 model came with Shoe Type 2 which was designed specifically with Olympus first ever TTL flash, Quick Auto 310. But you can make use of shoe Type 3 in combination with newer TTL flash T20 and T32. Confusing? Yeap especially when OM-1 is a mechanical SLR and I think it is kinda complicated for a relatively new OM user.

Within OM1 series bodies, you will find a few combinations of camera Models/Shoes. Accessory Shoe Type 1 (or early "FIX" type) has a single contact and permits non TTL normal auto flash and manual flash control. Accessory Shoe Type 2 & 3 are NOT usable with M1 or OM1 bodies as they have additional contacts and all those early OM bodies have no provision for such sockets.

Accessory Shoe Type 1 or early "Fix" Type shoe for M1 and OM-1's has no viewfinder ready light feature since they isn't any additional terminal apart from the main X-contact (F). Shown at left is a Accessory Shoe Type 2 designed for early OM-2 bodies for TTL flash with Quick Auto 310 flash, it has an additional contact at the hotshoe. The extra contact require an additional pin which make it not usable with any M1 or OM-1 bodies which has only a single input socket

(B) while early OM-2 bodies has two sockets (A). The OM1n model enjoys additional benefits with the new designs when used with Accessory Shoe Type 4 and OM2n bodies in particular, has full blown TTL flash capabilities when used in conjunction with T series flash. These bodies have one main socket and two inline pin inserts (E) which clearly illustrated from the top with two additional terminal contacts other than the main X-sync (C).

Important: Shoe 4 should be the correct shoe type for all OM-1n' bodies. It permits manual and normal flash control auto flash when used with T-series flash units (But in the case of OM2n bodies, TTL flash exposure control is possible); further, it will automatically sets X-sync at the shoe, and via a third contact to provide viewfinder flash ready/sufficient flash LED. Is it possible to use Accessory Shoe Type 1 or "Fix" type shoe on OM-1n bodies ? Why not ? Except that all additional features (other than X-sync) will not function. However, it is not possible to use the Two Pins, one main contact Pin Accessory Shoe Type 4 with any older M1 or OM1 bodies that has only one socket.

hotshoe.jpg socket.jpg

In most cases, by looking at the hotshoe we should be able to determine the model within a series. But since it is a removable type, that can be difficult to make a conclusion. Please take note of the sole pin inside the socket (2nd photo). The far right is a OM-2n accessory shoe socket with two extra pin inserts and it indicates it would require Shoe Type 4.

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Shared Resources: Supplementary articles: TTL Metering, Depth of Field, Shutter Speed & Aperture
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