The A Series filter holder and filters fit all 35mm SLR camera lenses with 36 thru 62mm diameter filter threads and Hasselblad (R) mount. A Series Filters require the use of the A Series Filter Holder. Diffractors. These filters have millions of engraved prismatic groves that, like a prism, diffract the light into its spectral colors without distorting the image. Whenever possible, this filter should be used with another filter to color or darken part of the picture. This will enhance the diffraction effect. Also, if you mount the camera on a tripod and use a time exposure longer than ? sec, you can obtain three concentric colored rings instead of the ray patterns. Simply turn the filter during the exposure.