Re: Bokeh, was Re: Direct negatives from slides

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From: Carl Weese (cweese@earthlink.net)
Date: 03/28/01-07:49:10 AM Z


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---------- >From: Sandy King <sanking@hubcap.clemson.edu> >To: alt-photo-process-l@sask.usask.ca >Subject: Bokeh, was Re: Direct negatives from slides >Date: Wed, Mar 28, 2001, 12:31 PM >

> Carl, > > Yes, I remember making that comment about the print from the 16 1/2" Dagor, > though I don't recall that you explained the effect as the result of bokeh. > So what is bokeh caused by, some kind of combination of lens aberrations > that makes the transition from in-to-out of focus smoother. > > Sandy King > > > >> >>Actually, you spontaneously commented on the excellent bokeh displayed by my >>16.5 inch A.O. dagor when looking at the picture of the overpass with sumac >>in the shadowed foreground. You noticed that the f/g looked wonderful even >>though it couldn't possibly be in focus: that's a perfect example of a lens >>with favorable bokeh characteristics. The smoothness of transition from >>in-focus to out effectively extends the depth of field. > > > > > Lenses with really >>awful out of focus character show a sudden, harsh transition. With strong >>selective focus, the blurred areas can look almost as weird as the >>donut-shapes you get with a mirror lens. In one example I saw, there was a >>liquor bottle in the background. In the lens with unfortunate bokeh, you >>could more or less tell it was a bottle. In the lens with beautiful bokeh, >>you could tell what brand it was because the logo, though blurred, was >>recognisable even though technical depth field was of course the same. Wish >>I remember where I saw that pairing. >> >>The first time I encountered the concept stated as such had nothing to do >>with Japan: Bill Pierce about ten years ago told me about a conversation >>he'd had, ten years earlier still, with the Leitz designer responsible for >>the Noctilux. What he said was simply that at f/1, invariably most of the >>picture will not be in the plane of good focus. So it makes sense to pay >>attention to the look of the out-of-focus image when designing the lens. In >>fact, I'd been aware of the difference on a gut level since the 1970's when >>I began using Leitz lenses for all my personal work even though I had a >>complete set of Nikons for commercial assignments. Art directors were happy >>with chromes from the Nikkor glass, but my b&w prints from Letiz lenses were >>invariably more pleasing, and this smoothness of focus transition is a vital >>element of the difference. But most of this work was in low light with >>lenses near wide-open. Most commercial work had artificial lighting and deep >>focus. >> >>With a 6x9cm stopped down to f/32, there won't really be any out of focus >>stuff unless your subject is quite close, within 4 or 5 feet I'd guess. >> >>---Carl > > >


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