Nikon FM2 - Manual (Page 63)

Filters
As is shown on the table, Nikon filters are broadly divided into
the screw-in, drop-in, and bayonet type. Because the FM2
incorporates a TTL full-aperture metering, the filter factor can
be ignored except in the case of the R60. For example, when
using the R60 in daylight, set the aperture three f/stops wider
than the figure indicated by the exposure meter.
Notes:
1) For lens protection, the NC filter is recommended.
2) When shooting a backlit subject or if there's a bright light source in the
frame, a ghost image is likely to result from the use of a filter. In this case,
you should take the picture without a filter.
Lens hoods
Recommended to prevent extraneous light from striking the
lens, Nikon's lens hoods come in four styles: screw-in, slip-on,
snap-on, and collapsible-rubber. Every lens should be fitted with
the lens hood specially designed for it. Note, however, that some
lens hoods can be used in common by several lenses.