Modern Classic SLRs Series :
Olympus OM-1 (n) - Part 2

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For any non-OM photographers, the most un-accustom way to handle an OM SLR camera is perhaps to notice the usual shutter speed dial has been replaced with film speed ring.

I would not like to speculate whether Olympus was duplicating Nikkormat's style by reallocating shutter speed scales to the front of the lens mount but I am quite certain the decision was very much contributory to the compactness of OM bodies even Nikon could not have done it so handsomely with their Nikkormat models way back in the 'mid '60.

<<-- The locking button (Red arrow) just next to the ASA dial has to be pressed in order to shift film speed value on the dial. It can be moved in either direction to set the desired ASA value. Also note the film advance lever is closely rest against the ASA dial.

The prominent film speed dial situated at most SLR's "usual" shutter speed ring with colorful popular film speed indexes painted in yellow will immediately captured one's attention. Such "strange" arrangement may, perhaps only apply to any non-OM users. But Olympus are not alone, other than the long discontinued Nikkormat, another uprising SLR competitors, Contax also adopted such design for their flagship model, Contax RTS series. So it is all a matter of preference, I think. Some may like it, but some would reject. The tiny button situated next to the Film Speed Dial is the Film Speed Dial Lock release button. The ASA value of the film is set by turning the dial while pressing the release button. This button ensures that the ASA dial is not turned accidentally. Film speeds from ASA 25 to 1,600 are marked to provide a quick visual guide for adjustment or confirmation. In order to achieve proper exposure with the metering guide provide by the camera's metering circuit, before using the camera for any photo session, one has to correctly setup a camera with the corresponding film speed in use. Understandably, by modern standard, OM1 series models has a relatively weak film speed range from ASA25* to 1600 but should be good enough even for professional usage (Come to think of it, if you still want to complaint, ask a question - HOW many of you use fast film such as ASA 1600 films that frequently ?).

* "ISO" values was not introduced and accepted universally as reference when OM-1 was introduced, thus, you will only see "ASA" (B) engraved on the film speed dial. The tiny button (See (C) is the film speed dial release button. If you want to change the film speed, you have to depress the button while turning the dial.

This device is for safeguarding accidental shifting of the film speed which may result in erroneous exposures. All values between ASA 25 to 1600 can be set in 1/3 increments. The shutter release button has a finger guide ring which has the film speed index (A) engraved at the edge which you should use it as the reference index.

But, you may ask - where is the manual shutter speed scales ? It is at a ring that surrounds the lens bayonet mount. It allows one hand operation of the aperture, focusing and shutter speed controls. 12 shutter speeds are marked from B to 1/1000 sec.

As with the Nikkormat and Contax SLRs, I don't regard it as the most convenient of all camera operations to set shutter speeds. But if you notice, Olympus has designed the OM-1 in such a way that the region around the lens mount is where the main gadgets of the camera/lens operations.

(A): Aperture; (B): Depth of Field Preview button (partially hidden in this photo); (C): Grip for shutter speed ring control (One on each side); (D): Mirror Lock up/Button. Lever; (E): Film Rewind Button/Multiple exposure disengaged button; (F): Lens release button; (G): PC Sync-terminal/Bulb settings; (H): Distance scale (Feet in orange, Meter in white); (i): Focusing and distance index; (J): Depth of Field Scales; (K): shutter speed index; (L): Manual Shutter Speeds control ring; (M): Focusing Ring; (N): Infrared Index

Using Exposure Meter

The exposure meter of the Olympus OM-1 camera is an orthodox CdS full-aperture type, reading the screen illumination by means of a pair of light sensitive sensors on either side of the viewfinder eyepiece. It is coupled to the aperture and shutter controls and the film speed setting. It has a switch on the camera top plate next to the rewind knob. When the switch is set to "OFF" or when the light level is too low for the meter to measure, the needle is removed from the viewfinder. The metering circuit requires battery to power the match needle display inside the viewfinder BUT the OM-1(n) will remain operative even if there is no battery installed or when its power has been completely depleted because it is essentially a mechanical camera.

OM-3Ti.jpg OM2000.jpg
Within the OM SLR series, there are four models namely, OM-1(n), OM-3, OM3Ti and an entry model OM model, OM-2000 are mechanical cameras.

<<<<-- OM-3Ti and OM-2000 are using LCD & LEDs display. While OM-1 remains as the sole model that used match needle system.

Normal procedure

A mechanical camera will have shutter speed and aperture value set to determine a theoretical 'good' exposure. Exposure guide is provided in the form of a match needle
* system used inside the viewfinder. However, unlike modern SLRs that has all the convenience (Like auto load, feeding and, auto film speed (DX) indexing etc.) to help you make less mistakes during setup your camera before shooting, all mechanical cameras required the user to handle these tasks manually. Before using the exposure meter, first check that the film speed has been correctly set. Turn the meter switch to "ON", frame and focus the picture in the viewfinder and select either the aperture or shutter speed at which you wish to shoot. This decision can be either be governed by personal consideration with preference on either depth-of-field control via aperture setting or controlling subject movement with shutter speeds selection.

* Match needle exposure display system was very popular among all camera manufacturers and it was not until second half of the '70, LEDs gains its popularity. By early '80, the trend has leaned towards energy efficient LCD which reputedly consumes only 1/10000th of the power of LEDs.

Although most would consider match needle exposure display system is rather 'primitive' but I think it is rather unfair to make such a remark as we are using a perspective of a user in year 2000 to review a metering system developed for a long discontinued SLR camera which is 30 years old. Anyway, personally, I would think it is still considered an excellent method for those whose preference is on simplicity on handling and it fits perfectly to a simple mechanical SLR such as OM-1(n). The display is easy to understand even for any beginners. All you need to know is: "+" is for overexposure, while the "-" is for underexposure. Just match the needle to the center either by adjusting the aperture on the lens OR move the shutter speed in front of the camera.

Also note the position of the needle in the viewfinder. It should be centered in the index. If it is not, adjust the aperture or shutter speed settings until it is*.

needle.gif Tips: It may be possible to 'fine-tune" adjustment of exposure reading by moving the aperture value (f/stop) on the lens to mid-settings between the apertures, but intermediate shutter speeds adjustment are not possible. The aperture ring on any Zuiko lens is designed to operate full stops with continuous adjustment between allow fine exposure adjustments.

If you cannot center the needle at your chosen aperture or shutter speed, correct exposure is impossible at that setting and you have to alter it. If the needle does not move at all, the battery is incorrectly loaded or is exhausted.

Clarification: In photography, you ought to understand there is NO such thing termed as "Correct Exposure". It is all a matter of personal preference and it is only matters IF you care and concern how others will 'judge' your work. So, if you are not bother by this, you will have only your personal satisfaction and desire to please - provided you know what you are doing when you trip the shutter release button. Anyway, unless you are using slide films, it is hard to make mistakes with today's modern film that has such forgiving exposure latitude.

Supplement: Just in case you are new to photography and must be wondering how the metering guide is provided inside the viewfinder which causes the needle moves - there is a pair of light sensitive CdS cells located on either side of the eyepiece that provide through-the-lens open aperture light measurement. There is a "ON-OFF" Switch located atop camera. The meter has a exposure range from a relatively weak EV 2-17 (ASA 100 with F1.4 50mm lens). Over the years, there are a few types of metering cells used for SLRs, the more commonly used cells are: Cds, SPCs, GPDs and SPDs.

Photocells generates varying electrical characteristic (e.g. current, voltage or resistance) when light is incident upon them. OM-1's Cds (Cadmium Sulfide (Cell) is a light dependent resistor rather than a cell, it is current-modulating light-sensing cell that was quite popular with lots of older cameras exposure metering system and external metering devices. However, it does not generate electrical current when lights hits them as with SPCs. Instead, current is being allowed to pass through the circuit when light hits the resistors.

The OM2(n) uses TWO pairs of cells, the additional pair, Silicon Blue Cells are located at the base of the mirror box. Silicon Blue Cells which more of less has the same characteristic as with SPC. Silicon cells is a light-sensitive substance which generates a minute current when exposed to light. They change the light energy into electrical current and amplify by circuit to a usable level for metering application. Both are very sensitive to light (as with the Gallium Photo Diode) without the need for filtration in infrared light levels.

SPC or GPDs has a far superior light reacting characteristic than Cds but as you can notice, most modern SLRs use SPD for their metering circuit as the SPD cell maintains a far more stable performance.But a more realistic answer could be, silicon based cells are generally less costly despite cells constructed from gallium arsenide are in principle more efficient when compared. Within my limited knowledge, that is all I know about metering cell.

<<-- The two Metering cells essentially controlling OTF metering used in the OM2(n) camera. The OM1's cells are nested in near the eyepiece and are not visible. Copyright ©-Free images collection, 2000 leofoo® Malaysian Internet Resources.

How reliable is the metering system employs in the OM-1(n) ? More than just good enough. Obviously you cannot use a modern perspective to judge a camera that was designed almost thirty years ago and expect a long discontinued camera to incorporate modern metering features such as Matrix multi-segment metering (No joke, I did come across such remarks in users group...).

meterillus1.gif meterillus2.gif
OM-1 bodies are employed with a popular center-weighted average metering system. It is safe and well proven to be an ideal metering method for most commonly encountered photographic scenes. But Olympus didn't think so, and their next generations of SLRs was offering multi-spots metering to allow photographers have even a greater control over difficult scenes. But generally, no one complaints, so do I, who felt it should be more than good enough.

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Credit: My old time buddy, Ahmad Ikram, Dr of Rubber Research Institute (RRI), Malaysia who shares the same passion with me and also lending his OM-1n, OM-4 and the Motor Drive 1 to me for preparing some images in this site; Mark Dapoz <>for reminding some broken links; Mr Poon of Foto Poon, Ipoh, Mr Richard, Ampang Park, Mr Lim and Miss Jenny of Foto Edar for their generosity for their OM1(n), OM2n camera and some Zuiko lenses. Mr Hans van Veluwen for mistakenly using some content earlier from his OM website; J Sorensen for providing some useful images to rectify some technical "flaws"; Mr Gen Holst for helping during the early stages of development of this OM site; Mr KKLow for some of his earlier images on the OM-1appeared in this website; Miss Wati and Mirza for helping me to convert this Operation Manual into a HTML format. Mr MCLau for rectifying some mistakes made on the earlier preview sites. Site created 'unfortunately' again with a PowerMac. A personal tribute to the creator of the OM system and also a site dedicated to all the fans of Olympuses and Zuiko Optics worldwide. Some of the content and images appeared in this site were scanned from OM official marketing leaflets, brochures and instruction manual(s) for educational purposes. Olympus is a registered tradename of Olympus Optical Inc., Japan.