This is my question in one huge breath:
What would be the correct size of an elliptic bokeh filter be to create a fake anamorphic distorted bokeh effect with a regular Canon 50mm f/1.8 II lens with a Canon EOS 550D (crop sensor of 1.6x, AF-S)?
Say what, elliptic bokeh, fake anamorphic?
Check this video to see an example of the fake bokeh. Notice the bokeh appears to be stretched vertically.
How can you make one?
Check this video for an example. The actual filter is shown at 0:36.
The basis is to draw an elliptic "slit" on the filter. I'd take it a step further in cutting some vinyl and taping it to the filter, to get a clean edge and no leaking light.
Why do I need you in this process?
I have no clue on what the best dimensions of this ellipse would be. Trial and error could work, but to what extent? It's optics, can't this be calculated?
You expect me to solve that just for you there?!
That would, of course, be great! Yet, I'm just as grateful for any and all pointers in the correct directions!