Nikon PhotomicF Tn Finder, Instruction Manual

20

Special Lens-Focusing Screen Combinations
Because the light-transmitting properties of some focusing screens differ from those
of ordinary screens, certain lensscreen combinations require exposure correction to
compensate for the influence of the screen. Compensating marks from -2 to +1/2
are engraved around the ASA film speed dial. Correct settings are given in the table
at right.
The numbers in the table indicate the exposure corrections to be made in f/stops:
this means you have to stop down or open up the lens diaphragm according to the
indicated numbers. With the Photomic FTN meter, however, exposure compensa-
tion is automatic at all aperture settings when the proper mark on the ASA scale

index ring is set opposite the film speed dial. If exposure correction is required, line up the proper marking opposite
the number corresponding to the film speed. For example, the table indicates a half-stop decrease (-1/2) for the
135mm f/3.5 lens with Type C screen. If the film speed is ASA 100, 1ine up the number 100 on the film speed dial
opposite—1/2 mark. When no exposure correction (0) is indicated, the ASA rating for the film m use should appear
opposite the red triangular index.

- Measure exposure by the full-aperture method.
- Use the stop-down measuring method.
- Neither method will work. With these lens-screen combinations the viewfinder can be used only for focusing,

not exposure measurement.

Combinations represented by a blank space are unusable because of image darkening or considerable moire over the
screen area.

EXPOSURE CORRECTION