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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!

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This can really be summed up as "What size hole do I use to make differently shaped bokeh?" –  rfusca Mar 7 '11 at 21:43
    
If you mean what dimensions as in what ratio of width to height for the ellipse, you could calculate it if you knew what film aspect ratio and final aspect ratio the anamorphic lens was designed for. Or you could just take a screenshot from a film and measure it in photoshop! –  Matt Grum Mar 7 '11 at 22:56

2 Answers 2

up vote 5 down vote accepted
  • Well "best" is an extremely subjective term and will largely be determined by individual taste.
  • In general, what you're describing sounds alot like a Bokeh Master
  • Your cutout must be at least smaller than the real aperture you'll be shooting at (shooting at, not the maximum for your lens). This is because you need it to become effectively the new aperture shape. If you're shooting at 50mm f/2 - then it must be at least smaller than 25mm across. If you have a 50mm f/1.8 and are shooting wide open, all the time - then its 50/1.8. If you have a 50mm f/1.8 lens and are shooting around f/2.8, then its 50/2.8. In order to keep as much light, you want it as large as possible without going over (focal length / f-stop).
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(This in case of f/1.8 -> I'm dslr-filming) Thanks for that! I think that pretty much sums it all up there. Correct if me I'm wrong, but, if you check how much "surface area" takes away from the original (focal length/1.8)-circle, you can also effectively calculate the light sensitivity decrease you should be expecting? –  user4192 Mar 7 '11 at 21:54
    
1.8 is only if you're filming with the aperture wide open. If you close it at all, its different. –  rfusca Mar 7 '11 at 21:55
    
Light sensitivity is probably the wrong word here, but by calculating the difference in the area before and after, you can determine the percentage of light lost, yes. –  rfusca Mar 7 '11 at 21:57
    
Be warned, you may be easily fooled when looking through the viewfinder about the bokeh, the lens hasn't stopped down yet (if you're not shooting wide open). –  rfusca Mar 7 '11 at 22:01
    
For the movie I'm going to shoot, I'd need a very shallow DOF pretty much constantly. Since I'm also going to stay in 1/30-1/50 zone, I'll need a some ND filters as well ;) But most of the scenes would be rather dark. Thanks for the help, rfusca! –  user4192 Mar 7 '11 at 22:06

The CineMorph filter does this elliptical bokeh method and also adds a streak element for flares on a rotating frame. There is a lot of footage and some with/without & before/after videos on the site here:

Originally designed for Run N Gun shooting where regular anamorphic lenses could not go! These filters will NOT stretch or squeeze to create a true anamorphic image. It keeps the image at 16:9 and you can crop in post at any ratio you choose.

It mimics characteristics of anamorphic lenses such as the flare or streak and vertically stretched bokeh. It's very easy to use and allows you to rack focus your photo lens like normal. This is a HUGE plus as shooting with real anamorphic attachments requires you to focus both the anamorphic lens and the photographic lens, making run and gun shooting pretty much impossible.

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Any chance you could post an example image? –  jrista Mar 28 '11 at 21:14

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