Modern Classic SLRs Series :
Nikon FM - The Shutter Mechanism

File Size: HTML Page (33k) Loading ...

The Copal Square Shutter

The core of the Nikon FM's shutter mechanism is the compact, all-metal Copal Square S focal-plane shutter which is not only well known for reliability and durability (The Nikkormat FT3 and EL2 used copal shutter as well - but it looked different, anyone can tell the difference ?). The shutter curtains (five blades in front, three at the back) traverse the film gate vertically, rather than horizontally (as is the case with conventional focal-plane shutters), and cover a distance of only 24mm instead of 36mm.

Copal Shutter.jpg (11k)
Shutter travel time is thus held to approximately 7 milliseconds only, thus enabling the FM to fully synchronize with electronic flash at speeds of up to 1/125 sec., may not to too impressive for today's standard, but during those era, it was the fastest in 35mm SLR photography.

Relative: Copal Square Shutter used in electronic Nikon EL2 and mechanical Nikkormat FT3.

This makes the camera able to take on the demands of synchro-sunlight shooting, with fairly low risk of ghost images caused by high ambient lighting (other than under very strong light source). The use of metal ensures lasting, dependable shutter operation in both the regular and motor-drive modes. On the other hand, noise and shock are all but well dampened by the incorporation into the shutter mechanism of a braking system and the use of an air-damped reflex mirror. All told, there are 11 shutter speeds available from 1 to 1/1000 sec.; B setting is provided for extra-long exposures.

Shutter release operation

The original FM has a mode selector (like the Nikon F2's shutter release lock) around the shutter release button. While the later upgrade in FM has remove this feature when the MD12 is made available.

ModeSelector.jpg (7k)3
For the first version, two modes are available in the mode selector: regular via the camera body's shutter release button and film advance lever, and motor drive via the triggering button of the MD-11/MD12 Motor Drive Unit.

In fact, this feature can help you to determine the rough timing of the version of the FM body in the used market - prior MD12 or earlier.

The FM's shutter release button itself is positioned for natural and unstrained finger contact, as well as coordinated operation with the film advance lever. The total shutter release stroke is 2.7mm, including a safety margin of 0.9mm, which is effectively assured by the shutter release finger guard; this helps prevent accidental triggering. Also, the button is threaded to accept both Nikon and ISO-type cable releases, including the AR series like AR-2 and AR-3, which are especially useful for critical shooting or for extra long exposures

* Note: (Applied to only the earlier version) The FM's shutter release mode selector which doubles as a finger guard. This click-stopped, safety-locked selector is knurled for positive and rapid changeover from regular to motor-drive operation, and vice versa; it is color-coded (black index for regular operation, red for motor drive) for added convenience. Note that in the motor drive position, the selector effectively locks regular shutter release operation and can be used for this purpose when a motor drive unit is not attached to the camera.

Shutter speed selection

The shutter speed dial is a dual function ring. It acts as a shutter speed selector ring as well as the film speed selection dial. The FM's shutter speed selector is click stopped and knurled for sure and easy manipulation. The dial's face is engraved with the 11 shutter speed settings provided: 1 for one second; 2, 4, 8, 15, 30, 60,125, 250, 500 and 1000 for fractional values of from 1/2 to 1/1000 sec.; B is also engraved. All these indications appear in white, except for 125 which is in red and indicates the maximum speed available for flash synchronization.


This is in the shape of a lever and can be used to trip the shutter after an intentional delay of up to approximately 10 seconds. To use the self-timer, advance the film, determine correct exposure by setting the aperture and shutter speed controls, then cock the self-timer lever by turning it away from the depth-of-field preview lever as far as it will go. The self-timer will start the moment the shutter release button is depressed.

A unique feature of the lever is that its setting is "cancelable" two ways. If the lever is cocked and the shutter release button has not yet been depressed, it can be turned back, if desired, and normal triggering operation can then be resumed. On the other hand, if the shutter release button has already been depressed, the self-timer's setting can still be canceled by simply turning it back; this action will complete shutter release. In addition to its usual role, too, of enabling the photographer to take self-portraits or join group shots, the self-timer has one other merit: the moment it is cocked, the mirror goes up immediately, thus ensuring that any possible camera vibration will have died out before the shutter fires approximately 10 seconds later.

For critical close-up photography, the sell-timer, in combination with a tripod (Cable release with lock feature), is particularly useful in preventing vibration, why ? Because to compensate the removal of the mirror-lock-up feature as available in the EL series. Nikon designed the FM/FE/FA series to flip the mirror upward first when the it is activated, thus, there will be NO reflex mirror mechanism involves, ONLY the shutter will open and close during the image capture process.

This reduces the vibration to the absolute minimal level. Care should be taken if behind the eyepiece has a strong light source, as the GPD photo sensors are located near the eyepiece, it might be affected and influenced light reading, just use a hand to cover the eyepiece when you are doing that.

PDF For detailed technical illustration of the action and time-lapse sequence in the coordination of mirror, diaphragm, and shutter operation. It is hard to put in HTML format, a PDF format is available for download (Credit: Shriro Technical Service Team) if you are interested.

| Next | Part 6/7

Index Page | Page 1 | Page 2 | Page 3 | Page 4 | Page 5 | Page 6 | Page 7 | Specification | Main Reference Map

First Section covers : Basic camera setup
2nd Section covers:
Optical Path | Viewfinder Screen
3rd Section covers: Its Metering | LED display/ADR
Earlier section covers: Metering
Method | The Metering Cells | related info on ASA Film Speed Settings
Last section covers:
Film advance lever, Film plane indicator, Film rewind, Frame counter, Multiple-exposure operation

| Back to Nikon FM's Index Page |
Back to Nikon FM Series Main Index Page |

Detailing its Basic Camera Operations (Instruction Manual)
Detailing its Technical Application of its features (6 parts)

| Message Board | for your favourite Nikon FM Series SLR models
| Message Board | for your Nikon Optics in a shared environment
| Message Board | Specifically for Dispose or Looking for Nikon/Nikkor Photographic Equipment

Standard production Nikon FM Series models:- Nikon FM | Nikon FM2 | Nikon FM2n | Nikon FM10 | Nikon FM3a |
Known variants:- Nikon FM Gold | Nikon FM2/T | Nikon FM2N Tropical Set | Nikon FM2/T Limited Edition | Nikon FM2N LAPITA | Nion FM2n Millennium 2000

Shared Resources: MD-11 | MD-12 | Focusing Screens | Titanium Shutter | Flash Units -SB-16 | SB-15 | SB-10 or other Options | Databack | Nikkor lens mount (related info)

Others:- Nikon AF-TTL Speedlights | SB-20 (1986) | SB-22 (1987) | SB-23 | SB-24 (1988) | SB-25 (1991/2) | SB-26 (1994) | SB-27(1997) | SB-28 (1997) | Nikon SB-29(s) (2000) | Nikon SB-30 (2003) | Nikon SB-600 (2004) | Nikon SB-800 (2003) Nikon AF-TTL Speedlight DX-Series: Nikon SB-28DX (1999) | SB-50DX (2001) | SB-80DX (2002)

Nikon BC-flash Series | Original Nikon Speedlight
SB-2 | SB-3 | SB-4 | SB-5 | SB-6 | SB-7E | SB-8E | SB-9 | SB-E | SB-10
| SB-12 | SB-14 | SB-140 UV-IR| SB-15 | SB16A | SB-17 | SB-18, SB-19 | SB-21A (SB-29) Macro flash | Flash Accesories | SF-1 Pilot Lamp

Instruction Manual: Nikon FM (HTML | PDF) | Nikon FM-10 (HTML) | Nikon FM2n's User's Manual available only in HTML format (6 parts) | Nikon FM3A (HTML)
Nikon FM, FM-10, FM2, FM2n and FM3A / Main Reference Map: (HTML) Nikon FM, FM2, FM-10, FM2n (Applicable to FM2T, FM2 "Year of the Dog"; Millennium 2000") and Nikon FM3A

weblibrary.gif   Nikon F | Nikon F2 | Nikon F3 | Nikon F4 | Nikon F5 | Nikon F6 | Nikkormat / Nikomat | Nikon FM | Nikon FE/ FA | Nikon EM/FG/FG20 | Nikon Digital SLRs | Nikon - Other models

Nikon Auto Focus Nikkor lenses:- Main Index Page
Nikon Manual Focus Nikkor lenses:- Fisheye-Nikkor Lenses - Circular | Full Frame | Ultrawides Lenses - 13mm15mm18mm20mm | Wideangle Lenses - 24mm28mm35mm | Standard Lenses - 45mm 50mm 58mm | Telephoto Lenses - 85mm105mm135mm180mm & 200mm | Super-Telephoto Lenses - 300mm 400mm 500mm 600mm 800mm 1200mm |

Nikkor Link.jpg

Index Page
  Special Application lenses:
Micro-Nikkor Lenses - 50mm~55mm -60mm 85mm -105mm 200mm Micro-Zoom 70-180mm
Perspective Control (PC) - 28mm 35mm PC-Micro 85mm
Dedicated Lenses for Nikon F3AF: AF 80mm f/2.8 | AF 200mm f/3.5 EDIF
Depth of Field Control (DC): 105mm 135mm
Medical Nikkor: 120mm 200mm
Reflex-Nikkor Lenses - 500mm 1000mm 2000mm
Others: Noct Nikkor | OP-Nikkor | UV Nikkor 55mm 105mm | Focusing Units | Bellows-Nikkor 105mm 135mm
Nikon Series E Lenses: 28mm35mm50mm100mm135mm | E-Series Zoom lenses: 36~72mm75~150mm70~210mm

MF Zoom-Nikkor Lenses: 25~50mm | 28~45mm | 28~50mm | 28~85mm | 35~70mm | 36~72mm E | 35~85mm | 35~105mm | 35~135mm | 35~200mm | 43~86mm | 50~135mm | 50~300mm | 70~210mm E | 75~150mm E | 80~200mm | 85~250mm | 100~300mm | 180~600mm | 200~400mm | 200~600mm | 360~1200mm | 1200~1700mm

Tele-Converters: TC-1 | TC-2 | TC-200 | TC-201 | TC-300 | TC-301 | TC-14 | TC-14A | TC-14B | TC-14C | TC-14E | TC-16 | TC-16A | TC-20E

Recommended links to understand more technical details related to the Nikkor F-mount and production Serial Number: by: my friend, Rick Oleson by: Hansen, Lars Holst

W A R N I N G: The New G-SERIES Nikkor lenses have no aperture ring on the lens, they CANNOT ADJUST APERTURES with any of these manual focus Nikon FE series SLR camera models; please ignore some portion of the content contained herein this site where it relates.

| Back | Main Index Page of Nikkor Resources
| Back | Main Index Page of Pictorial History of Nikon SLRs

| Message Board | for your Nikkor optics ("shared" because I do wish some of you to expose to other's perspective as well. Isn't it a sad sate to see photography has to be segmented into different camps from the use of various labels)

about this photographic web site

MIR Logo.gif
Home - Photography in Malaysia


Credit: To all the good people who has contributed their own experience, resources or those who are kind enough granting us permission to use their images appeared in this site. Mr. MCLau®, who has helped to rewrite some of the content appeared this site. Chuck Hester® who has been helping me all along with the development of all these Nikon websites;LarsHolst Hansen, 'Hawkeye' who shares the same passion I have; Ms Rissa, Sales manager from Nikon Corporation Malaysia for granting permission to use some of the official content; TedWengelaar,Holland who has helped to provide many useful input relating to older Nikkor lenses; Some of the references on production serial numbers used in this site were extracted from Roland Vink's website; HiuraShinsaku from Nikomat Club Japan. t is also a site to remember a long lost friend on the Net. Note:certain content and images appeared in this site were either scanned from official marketing leaflets, brochures, sales manuals or publications published by Nikon over the years and/or contribution from surfers who claimed originality of their work for educational purposes. The creator of the site will not be responsible for may discrepancies arise from such dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered tradename of Nikon Corporation Inc., Japan. Site made with an Apple IMac.