Vivitar 500mm Preset, Instruction Manual

Page: 8 / 12

-6-
SETTING THE STOP
Your 650-1300 lens has a changeable F-stop according to the focal length. (Non-auto-Iris lens) F-stop
according to the focal length is marked on the lens barrel. (Refer to the index for the distance and
diaphragm scale)
FOCUSING THE LENS
In order to get a sharp and clear image, look through the viewfinder of your camera, and then rotate the
focus ring which is marked “FAR <-> NEAR” until you can see a clear image through the viewfinder.
USING THE VIEWFINDER WITH THE TELEPHOTO LENSES
The effectiveness of different types of focusing screens varies with the focal length and maximum aperture
of the lens. The range finder of microgrid prisms built into the ground glass do not work as well with longer
focal length lenses as they do with the normal camera lens and most wide angle lenses, and may partially or
full blackout the center focusing spot. When such a condition exists, focusing is best done on the ground
glass portion of the viewing screen. On some SLR cameras, long telephoto lenses appear to produce a cutoff
image in the upper corners or along the entire upper edge of the viewfinder. Such viewing cutoff is actually
caused by the size of the camera’s mirror which is more adequate for the shorter focal length lenses only. The
exposed slide or negative will be unaffected by this viewing deficiency.