The heart of the COKIN Creative System is the filter-holder. Once attached to the lens, thanks to an adaptor ring, it can carry not only round and square filters but also modular accessories (modular hood, coupling rings etc...). The notches found both on the filter-holder and on the edge of round filters enable you to rotate the round filters to just the right position. Square filters slide within filter-holder slots in order to decentre special effects. For shorter focal lengths 20-24 or 28 mm as well as for wide-angle zooms (24-50 mm, 28-85 mm, 35-135 mm), System "P" is strongly recommended. It is available in diameters ranging from 48 to 82 mm and eliminates vignetting (dark edges).