50mm with most uniform bokeh (and a big front?)

redimp

redimp

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Feb 3, 2015
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Hey guys, I'm looking for a 50mm (45-60 range) rangefinder lens that would have the most uniform bokeh.

There is this effect that people refer to as "cat's eye bokeh" or "bokeh lemons", I also saw people call it "bokeh vignetting".

Essentially the front element of the lens is big enough to not cause vignetting of the image itself, but small enough to cause vignetting in bokeh, and sort of "cut off" specular highlights (bokeh balls).

This results in a certain effect that combined with field curvature creates a bokeh "swirl".

Field curvature, that also is sometimes referred to as "undercorrected petzval" is another effect that causes bokeh balls closer to the edge of the projected circle (and the frame) to distort and compress along the radial axis of the image circle.

I'm looking for a lens that does not have these effects, or has them well corrected.

I know that stopping down really helps to reduce it – because your entrance pupil gets smaller in correlation to the front element. There is this discussion I found that has a lot on the topic https://photo.stackexchange.com/questions/52126/what-is-the-cause-of-this-non-uniform-bokeh-effect

I am looking to adapt this lens to panasonic s1H, that's why I'm looking for a rangefidner lens to keep the setup compact, but if anyone knows of an SLR lens that fits the description please let me know.

So if the lens is slow-ish, like 50 2 or 50 2.8 I'm more then fine with it, even if it's a 50 3.5.

Another option is to get a very fast lens, like 1.2 that has a lot of aperture blades, and just stop it down to 2.4 or 4, but the aperture count has to be like 10+ to keep the bokeh round.

10096_SuwoO_1.jpg


I would appreciate any suggestions on the lens, I am also interested in longer focal lengths to make a set, something like 50, 80, 115, etc.

Thank you for your advice!
 
I don't have a specific suggestion but I wonder if lenses designed for a larger image circle might help. Like medium format lenses. That way you would potentially be cropping off the part of the image where the bokeh starts misbehaving...
 
I would recommend the 50 Elmar M f2.8 made around 1990 methinks
or the Sumnarit 50 2.5
Both render beautifully, soft bokeh, not swirly or over piwering in an Image
Will post photos when I get home
 
Somewhere there is a link to a site that shows bokeh of dozens of lenses. You can search through the examples and pick what you like.
 
Zeiss ZM C Sonnar 50mm f1.5. No cats eye, circular specular highlights, smooth and pleasant bokeh. The only issue is some chromatic aberration wide open and the focus shift at f1.5.
 
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