What are your general opinions about the major lens lines' bokeh (Nikon, Schneid er, Rodenstock and Fuji)? I like pictures with out of focus areas in them. How ever I hate those bright circles you can see when a picture has some tree in the background with strong backlight. If I buy a lens I would rather not have this flaw. Please state lenses with goo d bokeh as well as lens with bad out of focus characteristics. Thanks.
I almost hate to get into this because it's so variable, a matter of taste etc. But here goes....
It's been my experience that the German lenses tend to have signficantly bette r-looking out-of-focus areas than the Japanese lenses, but of course there are e xceptions.
If it's out of focus, you will always get those bright circles. My understanding of 'bad' bokeh is that an out-of-focus pinpoint of light will have greater density at the edges, so on a print it looks like a light doughnut.
I commonly see 'bad bokeh' from fast 35mm Nikon lenses used wide open, but it doesn't bother me in the slightest. I've never seen it in large format.
It's not often that I'm stumped on something like this. But I've never heard the term "bokeh" before. Is this something you all have just thought up?
Large format lenses as an average seem to have better bokeh than 35mm lenses. I think this is due to better quality control from lens to lens, and also to more aperture blades, creating a 'rounder' aperture. A perfectly round hole should have a very smooth diffracion pattern. When you use blades to create the aperture, you get diffration 'spikes' from the angled corners. You get two for every corner, radiating 180 degrees from each other radialy from the lens optical axis. If you have an even number of blades, you will have as many diffration spikes as you have aperture blades. If you have an odd number of blades, you will have twice as many diffration spikes. (even numbered apertures have the 180 degree spike superimposed on the opposite blades spike). You can easily see the spikes on bright points of light in photographs, especially when the lens is stopped way down. Even old LF lenses have many bladed apertures (20 or so), compared to 7 or 8 for your typical 35mm lens.
It seems to me that good Bokeh usually comes from the more symmetrical designs, as well as round apertures. Dagors, Summicrons, and Rapid Rectilinear show it to an extraordinary degree. I can't make up my mind about Tessars. Anyone? Anyone?
I believe bokeh characteristics involve a lot more than aperture shape.
For example, Leica 90mm R and M Summicrons exhibit identical bokeh and perform ance despite the fact that the M lens has many more blades and a much more round aperture.
Aperture shape does, however, show up in the rendition of out-of-focus specula r highlights that'll take on the shape of the aperture.
The little Olympus XA, with its H-shaped aperture at small apertures, did some pretty interesting things. <g>
The bokeh characteristic of many lenses that drives me wild with annoyance <g> is double-line bokeh. That's a situation in which an out-of-focus line is rende red as two fuzzy lines. As it's thrown more out of focus the lines don't seem to get significantly fuzzier, they just get farther apart.
Double-line bokeh is almost a hallmark of Nikon lenses. I had a 300 M-Nikkor t hat was nice and sharp but I ended up unloading it because of its double-line bo keh. Blurry separated tree trunks can be bothersome.
Otoh the little Fuji 250 I use as a WA on 8x10 doesn't bother me at all; the w ay it's used, everything's sharp.
Let's not let the Germans off the hook; many Zeiss Planars show some degree of double-line bokeh in out-of-focus background objects.
Schneider
There is a very good series of (Three) articles on the subject of "BOKEH" (From the Japanese katakana characters "bo" and "ke", which mean "out-of-focus blur") in theMay/June 1997 issue of Photo Techniques. (Back issues are available. Try 1 -800-877-5410 )
Harold Merklinger's artical was very enlightening to me. In it he determined tha t Over or Under correction of spherical aberation, go a long way in determining the Bokeh of a lens. Over corrected Lenses (Typical of lenses trying to be super sharp) yielded double line bokeh in the out of focus background. Under correcte d (Many clasic lenses i,e. Dagor) yielded very smooth (good) coherence in the ou t of focus background.
(P.S. I recommend Photo Techniques to any one in this LF Page)
Mike Phifer
If bokeh qualities are (at least partially) function of the aperture, wouldn't t he fact that most all modern lenses are mounted in Copal shutters make the comparison semi-moot?
Also since virtually all view camera lenses are mount ed in leaf shutters wouldn't this additional moving aperture create its own or modify the existing bokeh qualities of a lens?
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