Originally posted by Timbuctoo There's a PS Action called Glamblur that is a Soft Focus Action and does a very good job, so good that most time you wouldn't know if it was done with the lens or in PP. It allows you to see if a certain picture would be worth applying the effect to or not. I'm quite sure the K100D has a built in soft focus filter as well so that would be an option to, not sure about the K10D but maybe it has everything the K100D has. You'd be better off getting a 70mm limited lens and doing the Post Production.
IMHO, the effect of a real soft focus lens is very difficult to replicate digitally.
A real soft focus lens is a normal (read sharp) lens with a mean for the user to control the rendering of the lens, especially for the highlights, usually by adding a controlled amount of spherical aberration. With this kind of lens, it is always possible to shoot "normal" pictures, even wide open, by setting the "soft" control to 0. Some soft focus lenses for small format are the
Tamron SP 51A 70-150/2.8 soft focus zoom, the
Minolta AF 100 mm f/2.8 Soft Focus and the
Canon EF 135/2.8 Softfocus.
The so-called soft focus lenses comprising only one or two elements, like the Pentax SMC-K 85/2.2 Soft or SMC-FA 85/2.8 Soft, the M42 Portragon or the Lensbaby are very different animals. These lenses offer a mushy "dreamy" rendering when used wide open, with very soft corners and a relatively sharper center, due to the huge amount of uncorrected aberrations generated by their crude optical system. It is not possible to control this effect, except by stopping down the lens (and by tilting it in the case of the Lensbaby). Usually the effect disappears around f/5.6-8, but the lens never becomes as sharp as a better corrected lens. Of course, the soft effect of a one or two-element lens is very easy to replicate in Photoshop, but not the effect of a real soft focus lens.
Here are some pictures taken with my Tamron 51A, using different softness settings:
Cheers,