This is the Mir 20mm f2.5. It is an ultra-wide angle lens, which does fairly well in low light and has an overall flatness, which colorists will respect, since they will have more of a flexibility to make the color of the film look in any which way that they please.
This lens covers full frame, Super 35mm and Micro 4/3. It natively has a Pentax K mount, but has a sturdy EF adapter attached instead .