Originally posted by dragonfly
Doesn't the camera give you access to f stops that aren't available on the aperture ring?
Aperture rings usually have some mechanism to hold them at certain f stops. You get all the full stops (1.4, 2, 2.8, 4, 5.6, etc.) and most of the time, half-stops. The ring keeps moving the blades continuously so maybe you could set it in between some positions, or disable the holding mechanism and set an infinite number of apertures.
When the camera can control the aperture (KA or newer mount), the settings you can use are whatever the camera body can use. All the Pentax DSLRs can be set to use 1/3 stop increments or 1/2 stop increments. Since you can only choose one, you might gain f2.2 and f2.5 but lose f2.4. So more, but less.