The Flow Chart of how AMP Matrix Metering works.

Circuit Operation Outlined

The basic circuit formation of the FA is similar to that of the FG, but the introduction of the automatic multi-pattern metering (MAP) has added some features including A/D converter, or microcomputer unit (MCU) as the digital data processing devices.

1. Exposure data input block

(a) Metering data input. This block is devided into the automatic multi-pattern metering (AMP) and aperture/shutter-speed control. For the AMP, it is necessary to input the five brightness analog values from the SPDs into the MCU with the help of D/A converter and the five comparators. For aperture/shutter-speed control, only the brightness value of center area is utilized.

(b) Other data input. The following exposure data of digital, amount as the gray code are inputted into the MCU via the input selector.

Mode selected: 2-bit
Lens speed in use: 4-bit
Aperture selected: 2-bit
Focal length signal: 2-bit
EE lens signal: 1-bit
Film speed: 5-bit
Stop-down lever: 1-bit
Shutter dial: 4-bit

Turning exposure compensation swi tch on makes exposure compensation LED light up and the compensated film speed is inputted into the MCU.

2. Digital data Processing

The exposure data are processed in tile MCU with the control the clock of ceramic oscillator 524 Khz (= 219).

• a) Correct exposure value. Correct exposure value is obtained for the' AMP for the center-weighted metering as BV0;
• b) LCD readout. LCD readout value is processed for the different mode select and outputted at terminals 00 - 07 to drive LCD panel.

3) D/A conversion

Correct exposure value of digital is converted into a value analog in the D/A converter and utilized for shutter speed aperture opening control.

a) While metering

The correct exposure value (BV) is being compared with the brightness value (AV0) on a real-time basis. The MCU verifies and determines the correct exposure value (BV-AV0) to be equal to the real brightness value.

b) After shutter release

On P and S modes, the aperture control value determined by the MCU is converted into an analog value.

c) After mirror rising

On A, S and P modes, the shutter speed control value determined by the MCU is converted into an analog value. The TTL flash control value is-provided when ready-light lights up. Aperture and shutter speed control depends on the central brightness value, but also takes account of off-center brightness values by shifting the film speed value.

To realize Automatic Multi Pattern Metering (AMP) and accurately control the FA's complex functions, Nikon has developed one microcomputer and five IC chips to be used on the Nikon FA. Most of the ICs are protected with an coating of silicone from moisture and dust penetration. Technomodes/Aperture Controller (1): Commands digital switching system to properly execute mulV-mode auto-exposure operation; also assures precise aperture control. TTL Metering Amplifier/Shutter Speed Controller (2): BiMOS IC with five head amplifiers used for five-segment AMP sensors and one for TTL flash metering sensor; also controls stepless shutter speeds and TTL flash output control. Decoder Driver (3): Recalls encoded display data and sends it to the digital LCD readout in c/ear, digital form. Ceramic Oscillator (4): This 524.288kHz oscillator has the same capacity as those used in personal computers and other high-technology equipment. All shutter speeds used (Except in Shutter Priority AE, B and M250) was governed by the accuracy of the oscillator.

Digital IC (5):
Digitally controls 13 shutter speeds from 1/4000 sec. to 1 sec. in the Manual mode, complex and exacting operation timing for flawless execution in all modes, TTL flash sync speed, 16-sec. meter ON timer, as well as functions as a multiplexer to input lens data.

Microcomputer (6):
The FA's main command centre that does all computations for auto-exposure modes and flash sync speed; it also gives computations for metering and digital displays as well as controls the five IC chips with a 524.288kHz high-speed computation process.

D/A Converter (7):
Micro-computer controls 6-bit D/A converter to realize high-speed analog-to-digital conversion of the five segments' brightness values by high-speed sequential comparison method; D/A converter controlled by the microcomputer.

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Software changes in Micro-computer happened once in 1984 The software of micro-computer has been changed in order to improve the aperture stop-down linearity of exposure control and prevent the faulty open of mirror switch. This change has provided the main FPC with some modifications. l) Improvement of aperture stop-down linearity of exposure control The improvement ensures more accurate exposure control as shown in the graph below, but the reference value for shutter speed adjustment on A mode has been changed to 7.29.ms. Standard: 7.8lms F5.6 (+0EV) 7.29ms F5.6 (-0.l EV) 2) Prevention of faulty open of mirror switch. The base plate of resistor block and wiring of Mirror switch B255 have been changed in the new main FPC. New main FPC identification Sections have been covered with epoxy glass of green color in the new main FPC. A black dot has been marked on the base plate of resistor block of the former main FPC. New micro-computer has also been installed in some former main FPCs and they can be identified by a white colored identification mark on the Digital HIC.

Camera Instruction Manual - HTML | PDF (1.4 MB)
Main Reference Map for Body - HTML | PDF (731k)
Specifications - HTML | PDF (245k)

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

| Nikon FM series | Nikon FE series | Nikon FA |

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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.

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A contributing effort to Michael Liu's Classic Nikon SLR camera site.

Credit: Lars Holst Hansen who is co-maintaning the site; MClau, who patched a lot of mistakes for me on earlier stage of the site; Miss Rissa Chan - Marketing Manager and the members of technical service team of Shriro Malaysia (now Nkon Corporation Malaysia); Mr Terence HM Tan for his FA/MD15 images; Mr Victor for his Nikon FA body, EEwyn, my nephew for some of the scanning work; Mis Wati/Mis Mirza for their help on the OCR work on the instruction manual section - We all had some real good times on the construction of this site. Dave Hoyt who prepared the introductory page. Note:certain content and images appeared in this site were either scanned from official marketing leaflets, brochures published by Nikon and/or contribution from surfers who claimed originality of their own work to publish in this site based on educational merits. The creator of this site will not be responsible for any discrepancies that may arise from such possible dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered tradename of Nikon Corporation Inc., Japan. Made with an Apple IMac.Dedicated to a friend: 'JB' whom I have never met but remains a constant motivated force.