This article belongs completely to Ed Shapiro, a professional photographer, who contributed a lot to the art. It is based on the content of a topic of forum. I have to thank Ed for covering this topic. I could not find any place where Ed gathered and published his knowledge, so I decided to extend the audience of the forum where he posted this topic. So here it goes...
Soft focus is one of those sticky matters in portrait photography and in general photography as well. Years ago (in the 30s and 40s) there were virtual wars between the hard and soft focus advocates, so much so that the divided into camps, throwing harsh criticisms at each other in all kinds of art publications and at gallery showings. There were guys like Ansel Adams and the f/64 group who insisted that photography should be totally realistic with sharpness and depth of field up the yin-yang. In the opposing corner were folks like William Mortensen and other theatrical types who believed that photographers have a perfect right to tamper with Mother Nature and inject any sort of fantasy in their art. Mortensen himself used all kinds of soft focus and a multitude of darkroom techniques to create some of the most ethereal images I have ever seen coming out of a camera or an enlarger. He also invented the texture screen and the paper negative methods. If you can find his book “Monsters and Madonnas” you are in for a treat.
Soft focus, as with any other special optical effect is a matter of taste. In my pre-sitting consultations I brief my clients on the various approaches I can use in creating their portraits. In most cases they trust my judgment and allow me to do what I want.
With soft focus, unless you really want to create a very stylized effect, the rule of thumb is less is more. Oftentimes I simply use a piece of black netting to just “break up” the image very slightly to clean up the skin a bit. You also have to remember that a very diffused image might be ducky-dandy in a 4X5 proof or even in an 8X10 print, but will appear out of focus in a 16X20 or larger print. This is usually what bothers clients. You have to test your set of diffusers or the settings in your soft focus lens in order to know which ones to use when you are planning a higher degree of enlargement.
The rate of diffusion also needs to be appropriate for the subject. Grand dad alone in a portrait would probably need little or no diffusion; however when you add baby granddaughter to the image for Granddad to caress, a more diffuse image would impart a different mood to the scene. Diffusion has not only a cosmetic function but it is indeed a very effective tool that can add moods and feelings to certain scenarios.