The FG was the successor to the very simple Nikon EM camera of 1979. They both used the same ultra compact copper aluminum alloy chassis, pared down from the one introduced by the Nikon FM of 1977, but with differing outer cosmetic fiberglass reinforced polycarbonate plastic shells.
Nikon’s most recent 35 mm film SLR lenses, the AF Nikkor G type (introduced in 2000) lacking an aperture control ring; and the AF Nikkor DX type (2003) with image circles sized for Nikon's digital SLRs will mount but will not function properly. IX Nikkor lenses (1996), for Nikon's Advanced Photo System (APS) film SLRs, must not be mounted, as their rear elements will intrude far enough into the mirror box to cause damage.
Accessories for the FG included the Nikon MD-14 motor drive (automatic film advance up to 3.2 frames per second), the Nikon MF-15 databack (sequential numbering, time or date stamping on the film), and the Nikon SB-15 (guide number 82/25 (feet/meters) at ASA/ISO 100) and Nikon SB-16B (guide number 105/32 (feet/meters) at ASA/ISO 100) electronic flashes.
The FG was a battery-powered (two S76 or A76, or one 1/3N) electro-mechanically controlled, manual focus SLR with manual exposure control or aperture priority and programmed autoexposure. The FG was the first Nikon SLR to have programmed autoexposure. Instead of the photographer picking a shutter speed to freeze or blur motion and choosing a lens aperture f-stop to control depth of field (focus), the FG had a microprocessor computer programmed to automatically select a compromise exposure from light meter input. The FG was also Nippon Kogaku’s first amateur level SLR to have through-the-lens (TTL) off-the-film (OTF) electronic flash automation. Flash provides auxiliary light in dim situations. Precise flash exposure control for a natural look is complex and automatic TTL OTF flash metering plus thyristor electronic flash units were a fantastic boon when introduced by the Olympus OM-2 in 1976.
The FG used a match-diode exposure control system that lit LEDs along a vertical shutter speed scale on the right side of the viewfinder to indicate the readings of the built-in 60/40 percent centerweighted, silicon photodiode light meter versus the actual camera settings. The viewfinder also had a fixed focusing screen with Nikon’s standard 3 mm split image rangefinder and 1 mm microprism collar focusing aids plus 12 mm etched circle indicating the area of the meter centerweighting.
The major improvements of the FG compared to the EM were improved exterior cosmetics, internal printed circuit electronics, the addition of the manual exposure and programmed autoexposure modes, and provision for TTL flash automation. Although the FG had a much less advanced shutter than the more expensive Nikons of the day, it had a very sophisticated electronic design compared to earlier electromechanical Nikons. It would not be surpassed until the Nikon FA (1983) - for nearly three times the price.
The FG was Nippon Kogaku’s second SLR to tap this market (the Nikon EM was the first). Its very high level of automation, less durable internal mechanisms, and simplified manufacturing process were intended to attract new users to Nikon by providing convenience and low cost, rather than very high reliability. Its manual control capabilities plus more powerful accessories were intended to answer a major criticism of the EM (which had virtually no manual overrides) and allow those users to grow as they learned. The FG was accompanied by an expanded and redesigned line of the entry-level Nikon Series E lenses (discontinued circa 1987).
The FG also had one very rare feature for an electronically controlled camera. Nippon Kogaku’s philosophy that a camera must always work when called upon resulted in the FG’s backup ability to operate without batteries, albeit in a limited fashion. The FG, without batteries, had completely manual mechanical control with two shutter speeds (1/90th second, marked M90, or Bulb) and no light meter.
In 1984, a more spartan version of the FG, called the Nikon FG-20 was released. The FG-20 deleted the program mode and the TTL flash automation to attain a rock bottom price. The FG-20 was a technological retrograde step and not a commercial success. It was discontinued after less than one year.
Although it had numerically high sales figures compared to earlier Nikon models, the Nikon FG was ultimately not nearly as popular as competing programmed SLRs such as the Canon AE-1 Program (released 1981) the Minolta X-700 (released 1981) or the Pentax Super Program (in the USA/Canada; Super A, rest of the world; 1983). The FG and the Series E lenses were harshly criticized by many Nikon owners for not being as rugged and high quality as more advanced level Nikon equipment.
Nikon's venture into the consumer-priced SLR market with the EM, FG and FG-20 in the end proved to be a sales and marketing failure, and it is believed that Nikon actually lost money when factoring in development and tooling costs. None of the cameras sold to Nikon's expectation. The FG, and the Series E lenses with their lack of multicoating, were also criticized by Nikon owners for not being constructed to the standard of more advanced Nikon cameras and optics. In the years since its discontinuance, the FG has proven overall to be significantly less reliable than other higher-level Nikons (FE, FE-2, FM, FM2n, Nikkormat) of the day, particularly with respect to its electronics and shutter components, and this factor is reflected in lower resale values.