"81" series are color corrective filters that 'warm' bluish tones. They are avaible in several strengths (A, B, C & EF) with 'A' being the mildest warming effect.
•Available in all popular sizes.
Reviewed by 1 customers
Attached this warming filter for indoor portraits and cloudy outdoor pictures. I like the effect, it is very subtle. The lens quality appears very good. [...]