Cycles allows for photo-realistic rendering. Part of the realism comes from the simulation of photography parameters, such as lens, aperture size, and depth of field. When simulating anamorphic lens, there is something Cycles still miss which is anamorphic bokeh.
Generally speaking “bokeh” is the shape we see from far away blurred light sources. It’s more evident in night shots. When working with anamorphic lens (or when simulating them in Cycles) it’s important to stretch the bokeh according to the simulated lens.
In a normal close up scene the effect is subtle but gives an extra cinematographic effect. Compare this test-render from the Gooseberry Open Movie. From top to bottom we have a fisheye render, a fisheye render with anamorphic bokeh of 2.0, and fisheye render with anamorphic bokeh of 3.0:
Too subtle? Click on the images for a zoom-up version or look closely at the animated comparison:
Another shot, now with 1.0 (normal bokeh), 2.0, 3.0 and 10.0.
In cinema we often see works done with bokeh 1.33, 1.5 or for old movies 2.0. Nothing stops us from simulating other values as we demonstrated here.
This feature is aimed at Blender 2.72, so stay tuned and prepare your night shots. A special thank you for Aldo Zang for the help with the math part of the patch. Test scenes and feature request by Mathieu Auvrey.
Update: The patch is currently for review [here].