B+W's Series 8 Dark Red 022 Glass Filter is a filter for black and white film.
Compared to the lighter 090 red filter, this one even darkens the reds near the yellow tones in the spectrum, as its transparency only begins in the orange-red region. It produces dramatic effects and extreme tonal separation for graphic effects. That accounts for the large filter factor of approximately 8.
Each glass surface is vacuum coated with one layer of Anti-Reflection coating. This single layer helps to prevent internal ghosting and reflections. It also improves light transmission from approximately 92% (uncoated glass) to over 98%.
This filter uses B+W's Series mount made of brass. Filter glass, in mounts without threads, are placed into special holders and are held in place with a retaining ring or lens hood.