Canon Softmat filters are soft focus filters. Their soft-focus effect is due to the irregular surface of the filter which causes smaller details, like wrinkles and skin blemishes, to be out of focus while leaving larger details such as the eyes sharp. This filter is most effective when used for soft focus portraiture.
This filter is only available in 52 and 58mm, in grades 1 and 2, with 2 having the greater effect.