B+W 77mm IR Dark Red 092 Filter

The B+W 092 has become a popular filter for IR photography with digital SLR cameras. This nearly opaque filter looks dark purplish when held in front of a light source and blocks the visible spectrum up to 650 nm. It passes only 50% of the radiation just below 700 nm and from 730 nm to 2000 nm, transmission is greater than 90%. As the sensitization of IR films barely extends beyond 1000 nm, the red portion that is transmitted still makes a relevant contribution to the exposure. Effectiveness and filter factor are largely film and light dependent and individual testing is recommended.

Uncoated Glass
Uncoated glass is usually found with special effects filters and acrylic filters, where coating is either an impossibility or would work against the effect the filter is trying to attain.

B+W diopters use a thicker mount than the standard F-Pro mount, to allow for the thicker glass dimension used.