Just a quick demonstration of how using a moderate power close-up diopter (in this case a Vivitar +1) can not only allow longer focal length taking lenses at wide stops but give the much maligned Century Optics 1.33x anamorphic adapter the oval bokeh anamorphic junkies crave.
Normally you would not be able to use a 50mm taking lens at anything more open than f/5.6 without coma and softness.
This is a cheap, single-element close-up diopter so results will be even better with a doublet/achromat design. Coupling with the Tokina doublet, like I'm doing here (if I don't need infinity focus, I just leave it on), is a half-measure solution but it does make a big difference. Large diameter doublets are just very rare and expensive and don't, generally, come in the +1 power at 72mm and above.
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