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Albion Hockney

The "Swirly Bokeh" effect - early cinema lenses that have it?

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So most people are now familiar with this "swirly bokeh" effect. It is most famously very visible in the Helios 44-2 58mm Russian lens - and now Lomography has made the Petzval lens. After some research I found the effect can be traced back to older lens designs that didn't correct for Field Curvature. My knowledge doesn't go much pass that - and I was curious if anyone knew when lens designs started to correct for "field curvature" and if there are any sets of early cinema lenses that exhibit some of these effects. I was looking at tests of lenses like Super Baltars, Lomo's etc and I didn't notice too much of the effect - but it can be hard to find good tests.

 

 

 

for those unfamiliar here is a very clear example.

http://www.clickinmoms.com/blog/wp-content/uploads/2014/08/outdoor-portrait-by-Megan-Dill-840x560.jpg

 

 

EDIT: after seeing more tests - I have noticed the effect in both Cooke Speed Panchros and Kowa Prominar sphericals

Edited by Albion Hockney

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I got that effect once shooting wide-open on a C-series anamorphic lens but it was even weirder because the bokeh got stretched and curved into crescent moon shapes.

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Albion, you might be interested in a blog post I wrote comparing various cine lenses from the 20s to modern times, specifically looking at the out-of-focus characteristics:

 

http://cinetinker.blogspot.com.au/2013/10/comparing-lenses-blur-characteristics.html

 

There's a lot of internet conjecture about the causes of swirling bokeh, I can't say I have a definitive answer either, but the images in my post are interesting to study. I don't think the effect is limited to or caused by a particular lens family like Double Gauss, I'm pretty sure some C mount triplets had it too, but maybe the Double Gauss line is easily susceptible. Then again, you don't find it in modern Double Gauss derivatives like Zeiss Planars, which are used in many Zeiss cine lenses.

 

I think it's probably partly due to iris vignetting, which causes cat's eye shaped highlights that create the sense of ovals circling around the image centre. But mainly I think it's an astigmatic effect, where radial and tangential lines focus at different planes. These are normally somewhat corrected to meet in the plane (or curvature) of focus but depending on the design the out-of-focus areas may be much less blurred in the tangential direction, leading to a sense of circular motion. This correction is intimately linked with field curvature.

 

In the Alexa stills part of my blog post (the shots of a Bolex against a window) the Meyer Primoplan lens (from the 30s) shows the most obvious swirly bokeh, and you can see from the de-focussed projection image of that lens that the tangential lines are less blurred than the radial ones. Other lenses tend to blur in different ways. Some of the other older lenses, like the Schneider and the Speed Panchro, exhibit the cat's eye highlights, but don't seem as swirly as the Meyer. I haven't pulled apart a Primoplan to check, but from a Google search the Primoplan appears to be a Cooke Triplet derivative, not a Double Gauss.

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Hmm interesting, seems like there are a few different causes - and that basically the sharper lenses got the less it was apparent (however linked those two things are). I wish I had a wider focal length that was similar to the helios, because the helios is pretty decently sharp stopped down a bit and has a very strong version of the effect.

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I have done some work with very old lenses in order to produce the swirly bokeh.


The petzval lens design is well known to produce this effect and I have had good results with antique view camera lenses adapted to modern cameras like the Alexa.


My favorite is a voigtlander petzval from the 1860's that was made for a small view camera. Most of these lenses are of focal lengths of 135mm and longer with 160mm being common. I use two polarizers stacked one in front of the other in order to control exposure for day exteriors.


Here is a picture of one of the lenses I am working with:



Neal Norton

Director of Photography

Tampa, Florida

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Curvature of field is known since the middle 19th century when simple menisci were in use and two equal menisci forming a symmetric system eliminated it. Opticians or more specifically optics designers have always known what happens when you shift powers. Power is a general term for an optical element. Cooke also knew precisely what he was doing when he invented the triplet. Two cemented doublets in symmetry, even two cemented triplets in symmetry were very popular until WWII.

 

Not many photographers bothered about image parts out of focus because the strive was for sharp pictures for many decades. Not always much depth of sharpness but the content sharp. Differentiated pictures with parts in focus and parts out of focus came up after WWI, I’d say. High-key Hollywood shot at f/5.6, if possible. You’d have to cuddle with the série noire.

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