Modern Classic SLRs Series :
Nikon FM - Viewing Section
DOF and Its main reflex Mirror mechanism

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Depth-of-field (DOF) preview

Conveniently shaped in the form of a lever and positioned for easy, coordinated activation by either the right index or middle finger, this control, when pressed, 'stops down' (A photographic term which means close the iris diaphragm of the blades in the lens) the lens to its taking aperture.

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The photographer can then see exactly which elements of the picture will appear in sharp focus in the actual photograph, even though some of them may have appeared otherwise prior to pressing the lever. This is a clear departure from the mechanical Nikkormat FT series, where the DOF preview is via a button located at the top of the camera. It was not the first, the electronic Nikkormat EL series were already adopted this in 1972.

While the lever is kept pressed, the lens iris is not wide open (unless, of course, the photographer has set the lens to its maximum aperture); naturally, the image in the viewfinder 'darken' and will become even more so as smaller apertures (i.e., bigger f/numbers) are set. Note that you get more depth of field with smaller apertures. It should be mentioned that the selective use of depth of field through lens aperture manipulation, in accordance with any given picture-taking situation, is a significant camera operation since it is often closely connected with the creative effects that will be found in the actual picture. The FM's depth-of-field preview control has another function. It is used for stop-down (i.e., not at full aperture) exposure measurement with Nikkor lenses that do not have the AI (automatic aperture indexing, where a lens will automatically set to its largest aperture when mount to the camera for brightest possible image for view and focusing, stop down to the actual aperture value when you trip the shutter release button for an exposure) facility. This is an indispensable feature when you are frequently involved with creative depth of field priority assignments. For instance, close up, portraiture photography.

Reflex Mirror Mechanism

Although the FM is not the tiniest lot of the compact SLRs available in the market. But at its relatively compact body, it houses a very large reflex mirror in its main chamber. Employing a unique retraction system, the mirror's hinge mechanism moves back, then up, as the mirror itself flips out of the optical path when a picture is taken. This system, which was originally proven on the F2, has made it possible for the FM to employ a reflex mirror with a PO value
* (see illustration) that is substantially larger than what one would expect in such a compact camera. Note also how the aperture direct readout (ADR) works.

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The advantage of this extra-large size is that there is no image cutoff when the photographer uses a super-telephoto lens as long as 880mm or such close-up accessories as bellows and extension tubes for high magnification works. Noise and shock during the mirror's movement are further absorbed by the use of an air-damper in the mirror box. The mirror's back itself is specially treated to prevent flare-forming reflections off the back when the mirror is in the flip up position.

It should likewise be pointed out, too, that in motor-drive photography, it is the mirror mechanism that takes most of the punishment of the pounding motor drive. The FM's mirror mechanism, which is based on that of the reliable professional F2, is more than tough enough to take the demanding tension in motorized photography of up to 3.5 frames per second.

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However that since the FM omitted the a mirror lock up mechanism as with all the earlier Nikon (Including all the Nikkormat), some of the special lenses like the 6mm f/5.6 and 10mm f/5.6 fisheye Nikkor cannot be mounted onto the camera body.

| Next | Part 3/7

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
Earlier Section covers:
Optical Path | Viewfinder Screen
Next section covers: Its Metering | LED display/ADR | Metering Method | The Metering Cells | related info on ASA Film Speed Settings

| 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 |

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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

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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.