Modern Classic SLRs Series :
Nikon FM - Its Metering Part II

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Center-weighted metering

With its adoption of Nikon's center-weighted metering system, the FM assures the photographer of quite reliable TTL exposure control. In this system, the viewfinder screen's central 12mm diameter area is given a weight of approximately 60% in the reading, with 40% going to the surrounding area. In other words, the meter observes the brightness of the entire view field but concentrates its sensitivity on the center of the screen, since this is where the main subject of the vast majority of photographs is usually positioned.

Metering Illus.gif (7k)
This special design minimizes the possibility of the meter being misled by markedly brighter or darker areas elsewhere in the picture. The result is balanced exposures, regardless of how close or how far the subject is and whether the camera is held vertically or horizontally. One other advantage is the metering system always yield pretty good 'safe' results with lenses of any focal length, of cause, it is hard to compare with modern SLR's awesome metering capability, but it should be enough to handle most situations.

FRE and monolithic IC

The Functional Resistance Element incorporated into the FM's metering system is Nikon's own development. Consisting of an ultra-precise, metallic thin-film resistor on a hard glass base plate, it transmits to the meter the precise information on the ASA film speed set for the film loaded in the camera, the lens aperture selected and the shutter speed in use. Virtually impervious to changes in temperature and humidity (But not on drop test...), this important component has been made extra-durable by the use of gold alloy and other precious metals in its connecting taps and noise-free brushes.

FRE.gif (14k)
Like FRE, the IC (integrated circuit) used in the metering system is also Nikon-developed. It is no bigger than the head of a match, a mere 2mm x 3mm area, yet contains some 170 electronic components, including a bipolar transistor and a MOS FET (metal oxide semiconductor field-effect transistor).

Along with GPD and FRE, this IC, which has a monolithic construction, contributes to making the FM a compact, light, but truly high-performance camera.

FRE F3.jpg
Where it is difficult to illustrate how a FRE looks like in gray scale, I have missed out a couple of chances where a FM was sent in for servicing. Anyway, just to help you understand how the FRE looks, I took a picture of a FRE of the Nikon F3 and show you here.

GPD photo sensors

The FM's metering system uses two GPD's, which are virtually insensitive to i infrared rays and whose spectral sensitivity closely parallels that of the human eye, as its light sensors. The use of these elements enable the FM's meter to respond instantly to changing light levels of from EV 1 to EV 18. Thus, the photographer can shift from bright to dim-light shooting, or anywhere in between, then back again and be sure of consistent exposures throughout.
Mtering Circuit.jpg (5k)
ASA film speed

The ASA film speed selector is conveniently positioned coaxial with the shutter speed dial. The ASA range itself of 12 to 3200 is generous enough among compact 35mm SLR's

(The FM2n has boosted this to 6,400). For added convenience, the ASA dial has markings for intermediate ASA settings such as 64, 80, 125 and 160. The selector, on the other hand, is knurled for slip-free manipulation; a safety-lock is provided to prevent inadvertent changes in the ASA setting.

| Next | Part 5/7

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
Earlier section covers: Its Metering | LED display/ADR | Metering Method | The Metering Cells | related info on ASA Film Speed Settings
Next section covers:
The Copal Shutter, Shutter release operation, Shutter Speed selection, Self timer

| 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

| 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)

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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.