The Baader UBVRI Bessel I-Filter 31mm Photometric is suitable from f/15 to f/1.8. Classic photometric filter with transmission according to Bessel – parfocal with all Baader filters of the same size. Manufactured with most advanced ion beam coating technology / Daylight-Proof. Furthermore, its Reflex-Blocker™ hard coated and planeoptically polished with sealed coating edges (Life-Coat™). Blackened edges all around, with filter-lead-side-indicator in the form of a telescope-sided black outer rim. Equally suitable for modern CMOS cameras as well as for older CCD camera technologies.