New answers tagged bokeh
I'm the author of the article posted here previously: http://samluyk.com/homemade-petzval-bokeh/ If you have a fast lens, create a circular cover over it, and it should swirl the background. It's best seen with foliage: https://www.flickr.com/photos/samluyk/19365820681
I have never tried the following trick myself, but it seems to be a simple and very cheap alternative to buying yet another lens (yes, it's even cheaper than the Helios 44-2): Take a piece of light-proof paper, cut a hole in it. Attach it to the lens hood and put hood on lens. Swirly bokeh! See http://samluyk.com/homemade-petzval-bokeh/ and ...
This is a swirl-y bokeh, an often desirable flaw commonly found in some vintage lenses and lenses. There are some lenses known for this this characteristic, most notably the soviet made Zenit Helios 40-2 85mm F1.5 which is still being manufactured. You can find this lens on ebay for ~$600. If you are adventures enough you can convert the Cyclop night vision ...
To build on the other answers, this is indeed caused by a lens with undercorrected petzval. It is also vignetted, but more in one plane than the other. Here you can see a ray intercept plot for a large format tessar lens, these are also known as RIM plots or H'-TanU' Curves. On a RIM plot of the line is clipped, it indicates vignetting. You will notice ...
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