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How to Use Soft Focus Filters in Portrait Photography

Capture softer, more evocative images with classic filters
Photo of model with soft focus filter

Today’s cameras, lenses and sensors have gotten so good that images can now appear too sharp, almost too perfect. As a result, photographers have sought out ways to achieve softer, more evocative images. This is especially obvious in portraiture, in which the sharpness and clarity of modern optics reveal skin flaws that would not be noticed when the person is viewed in person.

This being the age of digital photography, there has been a shift to software solutions for softening effects, and there is no end of third-party programs and Photoshop techniques to break down an overly sharp image. Nonetheless, there is an argument to be made for shooting digitally with lens filters from the get-go, because let’s face it, who wants to spend more time in front of a computer screen if you can get the same result, or an even better result, from a filter placed over the camera lens?

But this is where it gets confusing. The softening filter world has become almost too nuanced, with manufacturers selling so many subtle effects it’s hard to keep it all straight. Adding to the confusion is the blurring of lines between cinema and still photography, each with differing filter starting points. Cinematographers have even been concerned with the switch to digital cameras, which give a certain “hard” or clinical look that seems to require some “softening” filtration to mimic the look of traditional movie film.

The Tiffen Company has brought clarity by separating filters according to three effects: halation, or glow around highlights; contrast reduction; and resolution (sharpness) reduction. Their extensive line has filters intended for only one of these three, and other filters that combine effects.

Note: The image at the top of this story is a shot of model, Katie, captured using a Zeiss Softer 2 filter over the lens. The proprietary design of these filters keeps details sharp but softens areas of low contrast, such as skin. Image © Michael Chiusano. Katie is from modeling agency Maggie, Inc., Boston, MA.

Photo of Lexi with fog filter
This is an image of model Lexi shot with a Tiffen #2 fog filter over the lens. The effect is noticeable for its strong reduction of contrast. © Michael Chiusano. Lexi is from modeling agency Maggie, Inc., Boston, MA.

The Traditional Approach

Still photography has relied on simple diffusion filters for many decades. A diffusion filter is an equal opportunity softening effect; it breaks down the image regardless of tonal differences.

The typical filter has a glass surface whose clarity has been cut down by sandblasting or other mechanical abrasion or scoring. This has the optical effect of diverting incoming light rays to a greater or lesser degree, thus blending fine details.

Image of female model no filter
This portfolio shot of Katie is straight out of the camera with no softening filter. © Michael Chiusano

At tonal borders between light and dark, the image will halate, with the light portion bleeding over into the dark portion. They also reduce contrast and lift black areas to a dark gray.

Another approach is to impose a random pattern of opaque pinpoint dots across an otherwise clear glass surface. This breaks up the incoming rays in roughly the same way, without causing as much halation. i.e., pure softening without the bleeding effect. Keep in mind that black dot diffusion filters cut down the light slightly and thus require a small exposure compensation.

Image of female model diffusion filter
This portfolio shot of Katie shows the softening of a mid-range diffusion filter. Skin tones record as a lot smoother and more pleasant than the “straight” shot. The effect is subtle enough that you don’t notice the effect unless you have a side-by-side comparison. © Michael Chiusano

Because the visual effect of diffusion depends on subject matter, these filters are often offered in graded sets, with the intensity of the effect varying in steps. The idea is to offer a filter that has almost no effect to a filter whose effect is extreme.

In my own experience, the filters “in the middle” are going to be your “go-to” filters; for a graded set ranging from 1 to 5, you are most likely to use grades 2 and 3, for example. Inasmuch as the cost of a full set is not minor, this approach makes a lot of sense.

Image of model black dot filter
Katie, again, only this time using a Schneider Black Dot filter over the lens. The effect is similar to a straight diffusion filter, but with less halation on highlights and higher contrast. © Michael Chiusano

Knowing which grade to use on a particular shot is a knack learned from experience; it’s hard to make clearcut rules. When I shot food for commercial clients, a touch of diffusion with a lower grade was really not noticeable, and added a slight enhancement by cutting the sharp edges of food.

For a portrait of an older woman, on the other hand, a stronger grade eliminated small wrinkles in the skin and saved retouching time. For an utmost painterly effect, what I call the “Hallmark card look,” you would choose the highest grades.

Image of model no filter
Here is a no-filter shot of Lexi. © Michael Chiusano

You can mimic commercial diffusion filters with any number of improvised home-brew techniques, and yes, smearing vaseline onto a UV filter will diffuse the image. So will wrapping the front of the lens with a plastic bag, held on by a rubber band. I’ve tried many of these things and offer no critique as long as you get a pleasing result. However, it’s not the same as using a repeatable, tested lens filter from a reputable manufacturer, and gaining knowledge of how they work time and time again with various subjects.

Image of model black dot filter
Here is Lexi with a black dot filter over the lens. It gives a subtle diffusion without much halation or contrast reduction. © Michael Chiusano

Fog and Smoke Filters

A close cousin to diffusion filters are fog filters. A fog filter is a diffusion filter added to glass that is not clear but infused with a slight white cast. The slight cast eliminates solid blacks in the image, lowers contrast noticeably, and thereby creates the look of an enveloping fog, hence the name.

It’s all about the halation rather than the blurring itself. Fog filters are also offered in graded sets of varying intensity but in general their effect starts where diffusion filters leave off. There is no mistaking their effect on the image, so caution is advised and there is no way to undo the effect in post-production.

Image of gas station fog filter
This Tiffen fog filter in a higher grade produces a realistic version of actual atmospheric fog. You would use this in landscapes more than in portraiture. The price of gasoline is a clue to the age of this image. © Michael Chiusano

Soft Focus Filters

Soft focus filters are an attempt to mimic the optical performance of soft focus lenses that were commonplace in the days of film photography and large format cameras. The goal of soft focus filters, and lenses too, is to blend (soften) slight tone differences while not touching areas of the photograph with great tonal difference.

In a portrait of a female, for example, a soft focus filter would blend skin tones, minimizing pores and irregularities, but maintain the sharpness of eyelashes and hair. In landscape work, a soft focus filter would blend sky tones but leave foreground details sharp and well defined. Unlike straight diffusion filters, soft focus diffusers aim to maintain image contrast and black tones.

A true soft focus filter is a lot more involved than simple diffusion and involves proprietary manufacturing technology; the two are not directly comparable. I use the Zeiss Softar in grades 1 and 2 and the design has been licensed to other companies. Cost is higher than the typical diffusion filter because of the optical innovation.

Image of sunflowers soft focus filter
The highlight halation of a straight diffusion filter enhances this photograph, giving it an evocative or romantic feeling. © Michael Chiusano

Final Thoughts

I think it is easy to get overwhelmed by the choices now available in the world of filtration. You can easily become paralyzed about taking a picture out of fear you aren’t using the “right” filter. Far better is to remember that your vision as a photographer is all that matters.

Editor’s note: The models featured in this story appear courtesy of Maggie Inc.

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