attention to the presence of the filter, especially with stronger grades, when diffusion is not required elsewhere. It may be desirable to lightly diffuse adjacent scenes or subjects, not otherwise needing it, to ensure that the stronger filtration, where needed, is not made obvious.
In diffusing faces, it is especially important that the eyes do not get overly soft and dull. This is the theory behind what might be called circular diffusion filters. A series of concentric circles, sometimes also having additional radial lines, are etched or cast into the surface of a clear filter. These patterns have the effect of selectively bending light in a somewhat more efficient way than nets, but in a more radial orientation. This requires that the center of the circular pattern is aligned with one of the subject's eyes, not always an easy, or possible, task, to keep it sharp. The rest of the image will exhibit the diffusion effect.
A variation on the
Another portrait diffusion type involves the use of small "dimples," or clear refracting shapes dispersed on an otherwise clear optical surface. They can be round or diamond- shaped. These are capable of more efficient selective diffusion than the net type, and have no requirement to be aligned with the subject's eye. They don't lower contrast, as by tinting shadows, as
Taking diffusion to yet another level, where keeping the existence of the filter from being readily apparent to the viewer is of paramount importance, is the Diffusion/FX® Series of filters. Available in Black and Gold Series, these are a combination of finely etched surface texture, with a unique pattern that maximizes the ability to reduce wrinkles and other fine details, with an internal pattern of very fine dots, which add subtle edge- diffraction effects. In addition, the Gold Diffusion/FX also incorporates a mild reduction of contrast, and a subtle gold “warming” tint, for improved skin tones.
The Glimmerglass is the first series of filters with a ‘psychological edge.’” Tiffen has developed the Glimmerglass series of filters for “making people look their best.” A new type of diffusion filter, the Glimmerglass subtly softens fine details in a unique manner, while adding a mild glow to highlights. As contrast is also reduced, the look is one of
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