Cokin diffusers have very little effect on the sharpness of the image they merely diffuse highlights thus reducing contrast as such diffusers can be used to soften a landscape or soften skin texture in a portrait to hide minor flaws cokin diffusers are available in three grades 1 830 2 840 and 3 850 with 3 having the greatest effect this filter measures 66 x 72mm and fits the cokin a series holder good for potraits improves the skin texture ideal for professional use