Opiates of the masses: bokeh
[2008-11-02] I have heard only one good argument for hunting marine mammals to extinction. It came from my friend Leo, who pointed out that mammals spent millions of years evolving from sea life – so what kind of perverse animal wants to go back to the ocean?
The idea of perversity comes to mind when people criticize current optics as being attacked as “too sharp,” “too contrasty,” or having “bad bokeh.” This seems to happen most with new rangefinder optics coming out of Leica and Zeiss.
As a preliminary matter, it is totally OK to buy a previous-generation lens because it is all one can afford (or all one wants to spend for a particular focal length). But now that we have that out of the way, let’s talk about the seals and the whales.
The inexorable tide of history
Query whether at any point in optical history any optical designer pulled back because a design exhibited too much sharpness, too much contrast or too little uncorrected spherical aberration. To the contrary, if Berthele, Berek or Mandler had been able to incorporate mass-produced aspherics, they no doubt have been building aspherical Summicrons and Summiluxes instead of Sonnars, Elmars or 35mm pre-aspherical Summicrons. By the standards of yesterday’s optical designers, today’s multicoated, aspherical, retrofocus wideangles would seem like gifts from the gods.
One can always dumb-down a lens that is sharp or contrasty by stopping it down until it diffracts, using a softening filter, diluting your developer, going down a grade in optical printing, changing the RAW development curve, or even simple mis-focusing. If you are consistently do the opposite of any (or all) of these, you probably really want a lens that is sharper and more contrasty. One would wager that of all of the Photoshop or Lightroom controls, the most popular are the ones that make pictures more snappy.
Some people would make the argument that lower-contrast optics maximize dynamic range on digital cameras, but this is an argument that only carries water in scenes with 500:1 contrast ratios – and even then would assume that anything of interest lay in the shadows (hint: take a look somehow how JPG compression is set up – to preserve highlight detail, which perceptually is where the interest generally is). Uniformly low-lighted scenes generally call for higher-contrast lenses because those scenes actually have a very limited brightness range.
Bokeh or baka?
If the justification for looking at old lenses is “bokeh,” question why it is even a concern. Bokeh seems to have become an end only in the past 15 years – and it is legitimate to question why it merits so much internet bandwidth. My personal observation, based on the existence of things like the Nikon Thousand and One Nights site, is that it originated in the nostalgia of some older photographers in Japan: “When I was 18, I really wanted a Nikon SP…”
But there are practical reasons to ignore the bokeh question altogether. First, most of the discussion of bokeh seems to revolve around the use of lenses 50mm and shorter (or 35mm or shorter on a camera with a crop factor) for purposes of taking close-range pictures. Many of these pictures just as easily could be taken with lenses twice as long at twice the distance (example: a portrait at a meter), Consider that:
– A 50mm lens (on a 35mm camera) at f/2 and a meter has a depth of field of 36mm (about 1.5 inches)
– A 90mm lens (on a 35mm camera) at f/2.8 and 1.8m has a depth of field of 50.6mm (about 2 inches). Even shot at f/2 (assuming it has that aperture), it would still have 36mm depth of field.
With a longer lens, one is not crowding human subjects or hitting their faces with the unflattering distortion that comes with short lenses. And we don’t see systemic complaints about bokeh with longer lenses (no doubt because with four or five elements they are less corrected in general), so if one has the light to use one, why not? What’s that you say? You don’t have enough light? Can’t afford a telephoto? Even if your only available optic is a short, fast, hypercorrected aspherical lens, the look of the background can be vastly improved by manipulating the relative distances from camera to subject and subject to background.
Second, many photographers appear to emphasize (and rely on) bokeh to make up for what are really severe compositional defects in photographs (point light sources in frame, relatively busy backgrounds, etc.). The use of bokeh for this purpose goes hand-in-hand with the “wide-open, close-up” school of photography that not only leans on bokeh to tidy up backgrounds but also uses shallow depth of field to increase interest in what ordinarily would be unremarkable subjects. Shooting with a camera on shutter priority is an excellent discplinary exercise. With far less conscious control over depth of field, one composes far more carefully.
Finally, perhaps best way to forget about bokeh as a factor is to ask oneself just how many of the great pictures in history were ruined due to bad bokeh. The answer is is, “none.” No one even thought of the concept until the late 20th century, and it is arguably more wrapped up in romanticism than anything that has ever been validated as sound photographic practice.