Nikon 25446B D90 User's Manual - Page 248

Compatible Lenses CPU lenses (particularly types G and D) are recommended for use with the D90. CPU lenses can be identified by the presence of CPU contacts, type G and D lenses by a letter on the lens barrel. Type G lenses are not equipped with a lens aperture ring. CPU contacts Aperture ring CPU lens Type G lens Type D lens A Calculating Picture Angle The size of the area exposed by a 35mm camera is 36 × 24 mm. The size of the area exposed by the D90, in contrast, is 23.6 × 15.8 mm, meaning that the picture angle of a 35mm camera is approximately 1.5 times that of the D90. The approximate focal length of lenses for the D90 in 35mm format can be calculated by multiplying the focal length of the lens by about 1.5. Picture size (35mm format) (36 × 24 mm) Lens Picture diagonal Picture size (D90) (23.6 × 15.8 mm) n Picture angle (35mm format) Picture angle (D90) A Lens f-number The f-number given in lens names is the maximum aperture of the lens. 228