The only difference between Nikon AF-D and AF-G lenses is that an AF-G type lens has no aperture ring.
Initially, the AF- G (the 'G' designation stands for genesis) specification appeared on entry level Nikkor lenses intended for the consumer market, because these lenses offer an number of benefits including being simpler to use, lighter, easier to construct, and therefore cheaper to mass produce.
However, Nikon has extended the inclusion of the AF-G specification to several new professional AF-S lenses and it is expected that this trend will continue across the Nikkor range as further lenses are introduced. According to statements from the Nikon Corporation market research has revealed that fewer and fewer photographers are using lens aperture rings, if their camera/lens combination has the ability to adjust exposures by 1/3-stop values electronically via the command dials, as this method is far more accurate than manual aperture ring adjustment, regardless of the photographer's experience.
G-type lenses, like all D-type Nikkor lenses, transmit focus distance information to the camera for 3D Matrix TTL metering systems, including flash exposure control.
However, the absence of an aperture ring does affect the functionality of the camera depending on the selected exposure mode; see the table below:
|Model / Exposure Mode||P*||S||A||M|
|D2 series, D1 series, D100, D70s, D70, D50, F6, F5, F100, F80, F75, F65, F55, F60, F50, F-401/S/X, PRONEA S, PRONEA 600i||Y||Y||Y||Y|
|F4, F90x, F90, F70, F-801, F-801s, F-601M||Y||Y||N||N|
|F-601, F-501, F301, F, F2, F3, F3AF, FE, FE2, FA, FM3a, FM2n, FM2, FM||N||N||N||N|
Y = Compatible
N = Incompatible**
* Includes Vari-Program and AUTO modes where these are available on the camera model in use
** It is possible to attach the lens to the camera. However, the aperture will remain open at its maximum value for viewing and TTL metering, whilst operating the camera's shutter will cause the aperture to close to its minimum value.
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