Saturday, June 28, 2008


A diffusion filter (also called a softening filter) softens subjects and generates a dreamy haze (see photon diffusion). This is most often used for portraits.

However, this also has the effect of reducing contrast, and the filters are designed, labeled, sold, and used for that purpose too.

There are many ways of accomplishing this effect, and thus filters from different manufacturers vary significantly.

The two primary approaches are to use some form of grid or netting in the filter, or to use something which is transparent but not optically sharp.

Both effects can be achieved in software, which can provide a very precise degree of control of the level of effect, however the "look" may be noticeably different.

Additionally, if there is too much contrast in a scene, the dynamic range of the digital image sensor or film may be exceeded, which post-processing cannot compensate for, so contrast reduction at the time of image capture may be called for.

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