Previously I had a quick look at how soft focus filters effect an image, and now it's time I had a comparative look at optical softening effects.
In the 19th and into the 20th centuries lenses made for Pictorialists were on offer. Many of these had distinctly soft image qualities when shot wide open. Browsing the Clarence White edited journal "Pictorial Photography in America" from 1920 thru 1922 reveals an interesting list of options, including -
- Aldis f/3 and f/4.5
- Goerz Portrait Hypar
- Pinkham and Smith -
- "Synthetic" for landscape
- "Visual Quality" for portraiture
- "Wolf Artistic" slip-on diffusion lens
- Spencer Portland Pictorial
- Struss Pictorial
- Turner Reich Hyperion Diffusion Portrait f/4
- Wollensak Verito f/4
There were, of course, other "Pictorialist" lenses manufactured over the years, including the color corrected Kodak Portrait lens series.
Interesting Note: In their guidance literature Kodak suggests pulling the focus on the subject to objects closest to the camera. Kodak said there was no useful information produced by their Portrait lenses on things in front of the point of focus. They suggest, too, letting the under-corrected spherical aberration and deep depth of field that comes with it keep things apparently in focus behind the nearest point focused on. This is something to keep in mind when shooting any under-corrected spherical aberration behind the point of focus lens.
More recently, small camera manufacturers have sold various "soft focus" lenses. I have a Pentax 85mm f/2.2 Soft in a Nikon F-mount. It's the only one I've ever seen configured this way. All the other f/2.2 Soft lenses I've seen come in Pentax' K-mount. In any event, this is the lens I would like to consider here.
The Pentax 85mm f/2.2 is a two element in front of the aperture meniscus lens. From prior use I know how strong the under-corrected spherical aberration is behind the point of focus from f/2.2 through to f/4. The effect is so strong that it is easily seen even on a rather small LC display.
Until I talked with a friend, I thought the super-strong softness of the Pentax was "just the way things were." He pointed out that at f/5.6 Pentax Soft images just started to "look good." His own work is much more subtle than mine has been up to now. He doesn't shoot for softness, he shoots to get the highlights to "glow", which is a rather different thing. The more of his images I see, the more I'm convinced his approach may be one of the best uses of soft focus lenses of any vintage and of any format, from large film to small APS-C digital sensors.
This led me to consider how the Pentax 85mm f/2.2 behaved down its aperture range. The following comparison shows the Nikon Nikkor 85mm f/1.8 K shot into the light wide open at f/1.8. Then I show the Pentax 85mm f/2.2 at each of its marked apertures.
As we can see, at f/2.2 the intense softness of the Pentax lens just about knocks you over. F/2.8 isn't much different. The level of softness is still very high. I'm not aware of a Pictorialist
era optic that produced this much under-corrected spherical aberration
behind the point of focus, though I've seen images taken with Wollensak
Verito lenses shot wide open where the softness is somewhat intense.
By f/5.6 the Pentax 35mm SLR lens is, indeed, "just starting" to look like my friends preferred rendition. The highlights start to "glow" while the underlying image begins to sharpen up. In fact, it has something of the Nikkor #2 Soft filter image effect in the highlights, except that the Pentax optics are still doing things to the edges of objects that filters would never do.
One of the other curious things about the lens is that it only stops down to f/5.6. It goes no further. So I am tempted to make a couple Waterhouse-like aperture disks to lay against the Pentax' aperture blades to see how the lens performs at f/8 and f/11. It could be an interesting experiment to see if I can get the corners to clean up a bit more while retaining the highlight "glow" that seems on promise.
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