The Schneider 4 x 5.65" Classic Black Soft Filter is a step heavier than Schneider's Black Frost effect. By using this filter, you eliminate the need for stacking filters together to achieve the desired degree of diffusion. For close-ups, it is terrific and aids in creating a seamless transition in the look and continuity from scene to scene.
The Double Classic Black Soft combines the features of the Schneider Classic Soft with a Black Frost 1/4. Highlights are flared, colors muted and reduced contrast. However, your blacks will still be rich and deep. This is a very useful combination of effects for 16mm and 35mm film, as well as for HD and standard video.
In the normal range of exposure, Classic Soft filters impart only a closely confined, very subtle glow to highlights. If large amounts of overexposure exist in a scene, like a "blown" window, Classic Soft filters add a stylish glow that keep the scene's contrast under control, while adding a romantic look.