Modern Classic SLRs Series :
Nikon FA - Part V - Metering System - Section 1 out of 2


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There are four metering options available in the FA: Center-Weighted, Stopped Down Metering, AMP (Automatic Multi Pattern - concept similar to the current "Matrix' Metering) and TTL OTF (Through the lens - Off the film) Flash metering.

AMP Illust.gif (3k)
The 'AMP' was termed 'revolutionary' because it was an innovative system while traditional mainstream metering method used were majority in center-weighted as the backbone. There were some variation such as partial or spot metering - which apparently Nikon doesn't favor The multi-spots metering introduced by the Olympus in their OM-3 and OM-4 in 1984 was considered 'innovative' enough as another (Incidentally, the company's also pioneered the TTL OTF metering for ambient and flash metering way back in 1975 first appeared in a Olympus OM-2n).

Thus, the metering system the FA has brought to the photographic world was truly amazing, it was crowned as the 'European Camera of the year' for such effort. Won't you agree with what you have noticed ? Virtually all the current Autofocus SLRs employ one way or another with such similar metering system. Some dubbed their 'modified' system as 'Evaluative-Metering', 'Honeycomb-Pattern', '8 segments Metering' etc..and even Nikon eventually altered and substituted the 'AMP' with a more technical name as "Matrix'. Currently, in the AF battle against its competition, Nikon still leads in terms of metering technologies and the AMP first used in the FA, may sounds 'primitive' after 15 years, but after such much refine and improvement, it has grown to be so sophisticated that it encompasses extended capabilities to flash, distance info and the amazing Nikon F5's RGB color matrix metering - but it was all started from the FA in 1983. To commemorate the Award of 'European Camera of the Year' and a double in Japan, "Grand Prix Camera of the year 1984", in a highly unusual fashion, Nikon introduced a Gold FA camera which is highly priced and treasure by collectors.

The dual metering system in center-weighted and AMP metering systems employ TTL full-aperture exposure metering. This means that light passing through the lens is measured at full aperture therefore the viewfinder image is at its brightest until the moment of exposure. As compared with the F4 or the F5, changing the metering modes can be set atop the viewfinder prism, the Nikon FA has a separate Metering Control Button which is locating just below the self-timer lever (Next to the lens mount). With this button, you can select or alter between the Automatic Multi-Pattern (Matrix) Metering or the Center-Weighted Metering. There wasn't any spot metering feature offers in the FA (If I can still recall, the first Nikon camera body that offers Spot metering was the F4 in 1988 (After this site, the next Site in PIM will be the F4, hehe...) and the next Nikon model was the F-801s that came 3 years later in 1991!). By the way, the Nikon FA and the Nikon F4 were the only two Nikon bodies that can still use the Matrix way of metering with just a minimum specification of AI (Automatic Indexing) Nikkor lens.

The 'default' center-weighted metering mode can be used in ALL the exposure modes in 'M', 'P', 'A' and 'S'. The AMP metering mode is usable in any automatic exposure mode either in 'P', 'A', or 'S'. If the metering control button is set to AMP and the shooting mode selector is in the 'M' position, the system will automatically switch to default system i.e. center-weighted metering. Well, the AMP requires a minimum spec of AI lens to activate. Originally, I have prepared the Nikkor Lens mount for the FA to illustrate the difference, but it ended up with more and have created a section on its own. For details, click here for more info.

OFF-TOPIC Supplements - Some Contradictory Views:
Date: Sun, 20 Aug 2000 03:37:27 +0880
Subject: Nikon FA camera AI-S lenses

Your description of Nikon FA camera signal pin does not mention this pin is connected to a two position switch. This switch controls which meter is in operation, AMP or Centre-Weighted With the pin in the out position, the meter is in AMP mode. With the pin depressed the meter is switched to Centre-Weighted mode. The signal notch on AI-S lenses does not depress this pin enabling AMP metering. AI lenses do not have this notch. When installed they depress the signal pin, shifting the camera to center- weighted metering. If owners of FA cameras prefer using AI lenses, then they limit their cameras to Centre-Weighted metering only. I hope these comments will contribute to all ready wonderful website.

Warren H. Hodson

Warren! - I am afraid you are quite wrong. The LENS TYPE SIGNAL PIN has nothing to do with the metering type (either AMP or Centre Weighted=CW). The LENS TYPE SIGNAL PIN has to do with the timing of the aperture stop down however. Necessary for AMP metering however is a MAXIMUM APERTURE INDEXING POST. All true AI lenses and newer has this. It engages with the MAXIMUM APERTURE INDEXING LEVER in the bottom of the mirror house. One can shift between AMP and CW by means of the "METERING CHANGEOVER SWITCH" in all modes but M (where only CW is available with any lens). - Lars-

Center-Weighted Metering Since the debut of the first Nikon SLR way back in 1959, there were a few Nikon bodies that are meterless (Like the bare bone Nikon F, F2, Nikkormat FS etc.), while some of them were using TTL average meter Nikon F Photomic, Nikkormat FT, but the first two Nikon bodies employed with TTL center-weighted 60/40 meter pattern was the Nikon F Photomic TN and Nikkormat FTn in 1967/8. Nikon always referred the Center-Weighted metering as their 'performance-proven' method because it has been introduced and used in many of their bodies since 1967 and it remains much the same today except changing the distribution ratio i.e. 60/40, 75/25, 80/20. The Nikon FA's center weighted metering was using 75/25 ratio in its center-weighted metering. The 12mm-diameter center circle in the FA's viewfinder outlines approx. 75% of where the priority was given in meter reading, while the rest of the viewfinder area shares the remaining 25%. This is also referred as the 'insurance buying' metering system. In most cases, exposures yielded can be regarded as above average and 'failsafe'. Anyway, don't ask me which system is more superior, any metering system will produce satisfactory results if the camera operator knows how to use it and recognizes its limitations. The millions of Nikon bodies have been around here for decades, the metering still yields good results, right ?

AMP (Automatic Multi Pattern) Metering The AMP was synonymous with Nikon FA that it overshadowed FA's many other equally impressive capabilities. Most people only like to remember or associate this Nikon's developed metering system directly with FA. How does this system works ? There are basically 2 SPD sensors with sectioned cells are used and the picture frame is divided into five segments (4 off-center areas and center area).

Rough Sketch.jpg
  A) AMP Metering Mode B) Center Weighted Metering Mode

At the P, S and A modes, AMP system divides the scene inside the frame into five segments and reads the brightness of each individual segment as shown in the figure. In accordance with the data of these segments, correct exposure is calculated to give optimum exposure automatically. Center of the frame surrounded by broken rinses is divided into 4 segments vertically and horizontally.

How does this system perform under various scenarios, combination with various Nikkor lenses ? (Three parts)

1) Lens speed compensation program: This program processes the five segmental SPD outputs to be fit for the real exposing condition on the film plane. Since the SPD outputs of off-center areas are subject to the effect of vignetting, they are compensated by the fo signal fed according to type of lens in use. Thus, when a lens in use can not feed fo signal to the camera body, the AMP is not operated. 2) AMP processing program: This program processes the five segmental SPD outputs and determine the correct exposure value. The SPD output of higher than EV 16 1/3 (ASA/ISO 100) will be removed.

When the following conditions are fulfilled, the AMP is operated.

1. Meter mode switch is off
2. Blank shots switch is off.
3. Stop-down switch is off.
4. Ready-light terminal is off.
5. P, S or A mode is selected.
6. fo signal is fed.

Metering range for Centre-Weighted metering: EV1 - EV20; Film speed range: ASA/ISO at ASA/ISO 100 with F1.4 lens; Film Speed range: ASA/ISO 12-4000
Automatic multi-pattern metering:
EV1 to EV16-1/3 at ASA/ISO 100 with 50mmf/1.4 lens.

The AMP metering is an original idea from Nikon. It hopes to resolve not only common photographic scenes but also complex metering situation where one has to based on experience or preferences to adjust exposure compensation. In a straight forward explanation, it is a metering system that automatically provides an optimum exposures for any
common picture scenario, while on the other hand, it will automatically compensate if any given contrast range in a five divided segments in the picture frame has a varying contrast. It segments the whole pictured scene and meters them in five areas - one corresponding to the viewfinder's 12 mm-diameter center circle and each of the viewfinder's four corner quadrants. The readings will then fed to the camera's CPU, where it is evaluated and compared by software developed with earlier input by Nikon engineers in the form of exposure scenarios that are stored in memory. Such inputs were based on ten of thousands of studied exposure readings on commonly taken scenarios. The ultimate goal is providing the photographer with an ultimate solution in exposure compensation without any complex calculation or lesser degree of exposure bracketing I received a mail which regarded the FA's AMP system as 'buggy, unreliable and producing mainly overexposed slides...'. The remarks really ate into my system for a while. Is the Nikon FA so terrible as described ? I have no problem with the FA's metering capabilities in the AMP, to be fair, I have not tried the camera under "extreme backlit, spot lit or adversely high contrast situations..." as claimed by the sender. Goohs, there are so many professionals out there testing camera ...but few has the knowledge that the FA has a conventional center-weighted metering system as standby, it can be switched over just by twisting a switch, that's all. Even if you have actuated the Depth of field lever by accident - in P and S modes it will changed into full-aperture center-weighted metering on A mode; A and M modes changed into stopped-down center weighted metering.

I am not suggesting the Nikon FA is the best camera in the world. Nor do I think it was such a lowly rated SLR in its own time. Here is another mail from a FA user in Holland, Gerben Boon, who gave a very neutral view on his experience with his camera. I have obtained his permission to publish his view -
* it deserves a good read.

But can you find any fault in the design of this camera ? Considering it was a sophisticated automatic manual focus SLR after the Nikon FG (1982) and obviously it came with heavy use of electronic. Generally, there were a few complaints and action to rectify them were swift and quick during the initial stages. Subsequently, there are updates and improvement. Cameras that produced after mid of 1984 should be considered very reliable and very few problems were reported. If you asked me to pick on something, yes. Just for an instance, the AMP's metering range was still considered very limited at EV1 to EV16-1/3 at ASA/ISO 100 with 50mmf/1.4 lens as compared with the center-weighted rather generous metering range of EV1- EV20.

AMP METERING SPDS FAIL TO READ CORRECT EXPOSURE AT LOW LIGHT CONDITION: Some camera bodies of the initial production stage have employed the SPD of inferior response at low light ' conditions as the AMP metering photo diode on the temporary basis and may cause the following deviations of exposure), this problem has been corrected immediately when it was found, models affected involve only a small quantity and it was replaced with the improved circuitry when affected bodies within the affected serial numbers camera were brought back even for general servicing. This was an positive move for Nikon to serve their devoted followers.

50mm f /1 4 ASA/ISO 100, Temperature: 35°C or lower


LCD Readout





1-1 sec

f5.6 or smaller


-1 EV


f5.6 or smaller


1/4 to 1 sec

-1 EV


Some camera bodies of the initial production stage have not been provided with a noise-proof cure and they may accidentally be affected by the electric noise of the particular speedlight units such as the SB-15 or SB-16 to cause an extreme underexposure.

Anyway, the AMP was the early test bed for today's sophisticated Matrix Metering employs in many Nikon AF cameras, you can safely regard the AMP as the first generation of the Matrix Metering used in all electronic Nikon bodies now. It is not a bad idea to go through the AMP in a detail explanation of how it works for future reference. Otherwise, 20 years down the road, you will only be reading through a line mentioning "the FA was the first Nikon that used the Matrix Metering system in 1983...". In 1988, five years after the Nikon FA was launched - the Nikon professional F4 was dubbed as the most 'light sensitive and flexible' F body ever. "Sensitive to light' because: For the first time, there are three metering system packed inside a professional Nikon F body. Metering system employed are Matrix, Center-Weighted and Spot Metering. "Flexible' because: It can used virtually any Nikkor Lens, yet retaining their respective original function i.e. If you have mounted a AF Nikkor, it autofocusing, besides, it takes non-AI Nikkors.

Hey, what is it got to do with the FA ? Oh.. sorry. The Nikon F4 has a vertical Matrix sensor on both sides of the eyepiece in the standard Multi-Mter Finder. When the camera is turned from horizontal to vertical position, the mercury switch enclosed in each of the two sensors is automatically activated, thus detecting the vertical position. When the sensor detects the vertical positioning of the camera, the metering output assignment of the five segments changes accordingly as shown below.

AMP1.jpg AMP2.jpg
So ? A top-of-the-line pro oriented camera model produced 5 years later in Nikon F4 created a basis for comparison. The Nikon FA users started to complaint - but Nikon has never produced any upgrade or updates for the FA. Obviously, after the the mid '80 - all manufacturers attention has shifted to AF models. Neither the F-801 came with this auto-switchable metering design and no one complaints much. Whatever, at least we can pick on something on the FA's metering.
To get yourself prepared, I have a flowchart/Block diagram in PDF format
for you to download (768k) and study it first. The AMP metering is quite complex and for those who may not be interested in following of how it functions, it may not be relevant to include into these pages. If you are, just click here will lead you to a separate section on AMP.

Relative: Nikon Focusing Screens for Nikon F, Nikon F3, Nikon F4, Nikon F5 & Screens for MF-Nikon Mid-compact Bodies and compare metering patterns used in the Nikon F4

Nikon F4's three metering systems are controlled by a control knob for the at the side of the metered prism. In a tricky situation where you have the time to do it, you can compare metered results yield by the various metering systems for a given scene. Similar way can be used with FA, it has ALL its modes operative in the center-weighted metering system, with P, S and A mode, both AMP and center weighted are available. You can compared the exposure data yields by both metering system if you like to just by simply depress the metering button while it is still in the AMP position (You need not to turn it) to check another reading by center-weighted metering system.

MeterSwitch.jpg (13k)
For a canon user, this lever can be misleading as this is their custom position for the depth of field preview button. In the FA, it is the Center-weighted metering changeover switch. Pushing this switch instantly changes the FA's metering system from Automatic Multi-Pattern Metering to centerweighted metering in the P, S or A mode. The changeover is automatic in the M (Manual) mode. Turning the switch outward, until a red indicator shows, locks the setting. Thus, you can switch between the dual metering to check a tricky exposure reading.

Another lever that could affect metering accuracy in the FA is the Eyepiece shutter. As the dual SPD sensors are located just next to eyepiece, this is indeed a convenient feature for unmanned shooting especially in situation where there is a strong light source behind the camera (Most common is position with the camera on the tripod and shooting downward with the sun at overhead), this device prevents stray light from entering the eyepiece and affecting the meter reading.

Eyepiece.jpg (8k)
The shutter blind is painted red so it's easy to tell when it's in use. The FA was the second automatic Nikon bodies after the F3 that provide with this feature. To operate, just push the lever (Red arrow). It is very much easier to operate than the F3's eyepiece shutter. Although the reasons given was convincing enough, but not all Nikon bodies incorporated with this neat feature. This is not 'original' idea, I remembered multimode Canon A-1 was the first to have this feature way back in 1976.

| Back | Next | The TTL OTF Flash Metering System

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Other Technical Issues: Part I | Part II

The AI-S Nikkors (related info | TTL OTF Flash Metering | Interchangeable Focusing Screens. The MD-15/MD12/MD11 Motor Drives | 3rd party Power Winder (new) | Flash Units -SB-16 | SB-15 | SB-10 | SB-16B & Other Options | Databacks | Titanium Shutter | Variation : Mr Y K Wong from Singapore contributing 11 images of his Nikon FA GOLD

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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

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