Lumicon 58mm Minus Violet Filter - LF3130
Lumicon Minus Violet and Infrared Blocking Filters are used primarily to "bracket" the color-corrected band of refracting telescopes. The Minus Violet and Infrared Blocking Filters can also be used as "visible" filters in RGBV (red-green-blue-visible) astrophotography with reflecting telescopes. The larger Minus Violet filters are for telephoto lenses.
Most digital/CCD cameras have built-in infrared filters, in which case either the Minus Violet or Infrared filter may be used. The choice would depend on how far into the blue your primary lens is color-corrected. The Minus Violet filter blocks wavelengths shorter than about 420nm; the Infrared filter blocks wavelengths shorter than about 400nm. If your camera does not have a built-in infrared filter, the Infrared Blocking Filter is recommended, which blocks all wavelengths longer than 750nm.
The LF3130, 58mm Minus Violet Filter, threads into 58mm telephoto lenses. The LF3130 may be used with other size lenses by using step-rings (see Step Rings, under Photographic Accessories) .