Nikon F25B manual Focusin G

FOCUSIN G-continued

Infrared Photography Film-Plane Indicator

The plane of sharpest focus for infrared light is slightly more distant than its counterpart for visible light as seen through the camera's viewfinder. Thus, for sharpest focus in infrared photography, adjustments must be made.

To compensate for this shift in focus, first focus the im- age sharp ly through the viewfinder. Then, turn the fo- cusing ring counterclockw ise until the point focused is aligned with the red dot (or line) provided on the lens barrel. For example, in the picture below, the lens has been focused for infinity (00) infrared shooting. Note that when lenses having a focal length of 50mm or less are used stopped down to f/8 or below, no adjustment is necessary due to the large depth of field avai lable.

Note: Some new optics using Nikon's Extra-low Dispersion (ED) glass, as well as reflex (catadioptric) lenses , do not require refocusing for infrared photography. Refer to individual len s instruction manuals for details.

Under various precision shooting situations, such as close-up photography, it is often necessary to measure the film-to-subject distance to ensure the sharpest focus . Th e camera's film plane is indicated by the top edge of the figures making up the serial number at the upper left of the camera body. Note that these figures are 46.5mm from the front surface of the camera's lens mounting flange.

(mounting flange front surface)

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