The Cokin A123 filter allows coloring of part of the photo.One half of the filter is neutral, the other half is blue.The transition between them is smooth, so you will not see a clear color border.The gradient starts in the middle of the filter and the blue half is darker than in version B1 (Filter A122).Cokin filters are mounted using a holder (holder), which is attached to replaceable mounting adapters, with diameters that can be adapted to your lens.System A (size S) is recommended for use with compact cameras with lens filters or amateur video cameras.