Every lens manufacturer wants their potential customers and users to know how wonderfully sharp their lenses are. Great pains are taken to tweak all aspects of things technical to correct any that need be tamed to make wonderfully crisp images; spherical and color aberrations, coma, astigmatism, etc. So, if we crave the ultra sharp, why wouldn’t we simply want every image to be really “sharp”?
To be or not to be–sharp
Some subjects are sharpness dependent, for without detail the image is lost. Macro photos of things like insects, big subjects like landscapes, architectural with building details, medical, fashion, and even photojournalism images. But, some subjects are more about mood and color and expression than fine detail, like portraits and glamour type images. Sometimes sharp is simply TMI, or “too much information”.
The “soft effect” goal is to reduce or minimize the rough edges of sensitive subjects, yet preserve enough detail to make the image look intentional. Every soft effect image is a combination of a sharp image and a non-sharp image. Otherwise, without the correctly executed, accurately focused sharp image, all you have is…a blurry and unsharp (and likely useless) image. Of course, there are many things that prevent an image from being sharp, and accordingly, there are many ways to make a “soft effect” image, depending upon which aberration you choose to combine with your sharp image!
From practical experience as photographers, we’ve seen our mistakes and know how such things as incorrect focus or camera motion ruthlessly steal sharpness. We also might know that lenses have their best apertures for sharpness and many not be as sharp wide open due to “spherical aberration”. This phenomenon is the result of how the center of a lens can focus on a different plane than at the edges. We might have experienced how shooting through a dirty window or a screen makes things look much “softer”. Every one of these things could artfully combine with a sharply focused image, and with the right lens design or attached filter can make a pleasing soft effect image.
History of Soft Effect
For many years, the natural softness of primitive large format lenses were in effect the first “soft effect’ lenses. By careful placement of the part of the image that was crucial in the portion of the image circle that was usable, the rest of the image went soft due to uncorrected spherical aberration.
But lens/camera manufacturers created more exacting methods by building aberrations into key products for their own dreamy looking offerings. Rodenstock’s Imagon lenses were early 1920s offerings of the Anachromat Kühn lens, later called the Tiefenbildner-Imagon (depth of field creator). It used a simple two-element lens, uncorrected for spherical aberration, and further controlled softness/sharpness with the use of “diffusion discs”, or apertures punched into holes surrounding the central open window. The soft effect could be modified by selecting how much of the outer ring of holes would admit light, and increase the “out-of-focus” component when combined with the sharper central area’s image.
Many other camera manufacturers followed suit with their own “soft effect” lenses, including Leica’s Thambar 90mm f2.2, Canon’s EF 135mm lens f/2.8 with Softfocus, Pentax SMC 28mm f2.8 FA Soft Lens, Mamiya’s 180mm Soft Effect portrait lens (sharp at ƒ8 or greater but increasingly softer towards wide open; also controllable with Imagon like discs), to the more recent Lensbaby Velvet 56mm lens.
Home Made FX
Photographers have over the years invented their own personal effects like nylon stockings pulled over the lens front with the mesh’s centers burned out with cigarettes. The result was part sharp in the center, part soft at the edge. Officially manufactured versions of this effect were made in abundance.
The same situation was created with smeared petroleum jelly on a filter over the lens, strategically leaving part of the image sharp, or the “Penthouse effect”, after owner/publisher Bob Guccione made a practice of using this method to create dreamy looking nudes.
The Current Crop of Commercial Soft Effect Filters
Many filter manufactures formalized a process of sealing a black or white mesh within a glass or plastic filter, using the softening effect of diffraction combined with the unaffected area to produce a high or low key soft effect. These dark “fishnets” will not affect the image’s contrast, where a white translucent mesh will lighten shadows, creating a higher key effect. Such filters were made by a myriad of manufacturers, including Tiffen, Schneider, Hoya, and Cokin, etc.
Hasselblad created a filter called the “Softar”, which consisted of a flat glass filter with small “lenslets” manufactured upon it. It allows the “soft effect” to be present regardless of the ƒstop used, as the effect was not aperture dependent. The depth-of-field of the main lens didn’t affect how the filter presented the image to the light-sensitive surface-film or sensor, as the “lenslets’ created images of a different focal length which combined with that of the main lens.
More recently, Schneider Optics made (and still makes) a version of this called “Classic Soft”, which is similar in function to the “Softar”, but made in sheets that are designed to drop into compendium shades, as well as screw in types for SLRs.
It’s important to note that using lenslets, the effects are format dependent! Filters designed for the 6cmx6cm format and lens flange to focus plane distances of the like have a spatial frequency lenslet focal length that doesn’t precisely produce the same effect on 35mm form factor cameras. The Schneider Classic Soft is engineered for 35mm motion picture cameras, far closer to 35mm SLRs than the medium format versions, and are also sold in screw-in versions specifically made for 35mm SLRs. Other versions include Kenko’s Realpro Softon A.
Another type of filter has etched plastic or glass to refract a part of the image. These include Hoya’s “Diffuser”, which has two variants; the diffuser and the DUTO (which has concentric lines etched into the filter’s surface, Kenko’s versions of the same).
Nikon created a filter many years ago with silver particles dispersed into the filter’s glass. Its unique effect was created by both diffractions around the silver particles as well as randomly reflected light from the silver slivers themselves (say that five times fast).
As with most of these manufactured filters, they were available in multiple strengths; Nikon’s in 2 versions, Hasselblad’s “Softar” in 3, for instance.
Here are some examples of the effects of various “soft effect” filters. Filters used are the Hasselblad Softar II, and a group of Tiffen Hollywood Effects filters: Warm Center Spot, Pro Mist 5, Warm Pro-Mist 5, Pro-Black Mist 5, and Warm Soft/FX 5. The Softar, using lenslets as previously mentioned, was made available in two strengths (I and II). Similarly, the Warm Soft/FX does as well, with smaller irregularly shaped lenslets, as well as a slight orange color to add warmth. The Pro Mists are small particulate coatings of either light or dark particles; the former adding some lightening effect on shadows (for a more high key effect), and the latter being more contrast neutral. Some of these filters might not be available new anymore. Tiffen has continuously modified their filter selection based on format and market needs, but the basic principles using the effects of particles and lenslets will still apply. The Tiffen FX filters were available in multiple strengths. I chose the highest level for the illustration.
In this set, we can examine the effect on a subject or object. I used a model that had both a flexible schedule and posing capability :)
Soft focus filters
In this next set, the same filters used will show their effect on a light source itself, which is valuable for how these filter effect the capture of both light sources and specular reflections within an image.
Filter effect on sources & reflections
Soft Effect in Post
There is a myriad of post-processing techniques to attempt to duplicate the various soft effects created by either the dedicated lenses or the filters designed for soft-effect. Gaussian blurs in various blending modes, surface blurs, etc. when combined with the original layer can approach the look of a “Softar” filter, but simply using a soft effect filter over the lens is a very time efficient way of producing this effect….rather than work in post in a processing application like Photoshop.
The closest that I’ve seen a post-process solution has come to the look of lenslets (Softar type) is Eddie Tapp’s “Monte Zucker Dream Glow”, using multiple layers of varying opacities, blended separately in both lightening and darkening modes on the same layer.
But ultimately, if you know in advance that your subject would benefit from a “soft effect” image, then there’s nothing that beats the speed of simply adding one of the appropriate soft effect filters to the lens when shooting. That’s why these filters still have a useful life in the world of digital photography.