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fisheye (equiangular) lens- Motion tracking and image stabilizing


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#1 thomas-english

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Posted 17 June 2009 - 05:20 AM

I am a cameraman rather than a VFX er. So please excuse the novice approach to this question.

We are shooting fulldome footage for display in planetariums. We are using 180° to 220° lenses that are equiangular mapped (i.e. mathematically approximate fisheyes). One of the great problems with fuldome is the quest for maximum image stability as any camera shake really does move your world.

Under normal circumstances gyro's and heavy grip is suitable. I am currently planning a skydive shoot were these will be impossible. Please can you point me in the correct direction for research to image stabilize across equiangular mapping rather than the normal gnomic mapping normal lenses are. (i.e. a flat plane). In other words I want to image to distort as it moves across the image.

The issue is that these lenses are 180° or more. So I can't see the standard workflow of making an undistorted image, motion track/stabilize, re-distort working.

I suppose I am having issues getting my head around this a little so I am hoping someone on this forum might say something that will just click the knot in my brain.

Thank you.
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#2 Scott Fritzshall

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Posted 17 June 2009 - 02:10 PM

Could you elaborate a bit more on what exactly you want to stabilize? If you're jumping out of a plane with a camera strapped to your body, I'd imagine that the image would be pretty shaky to begin with. Are you just looking to remove gate weave or small high-frequency vibrations, or are you trying to do something much more drastic, like taking the skydiving footage and smoothing it out completely to remove the sense that the camera was basically handheld?

Lens distortion is always kind of a tricky thing. I do know that there are models for dealing with fisheye distortion- take a look at the bottom of the Examples page for PTLens, which is a Photoshop plugin that does a pretty decent job at removing lens distortion: http://epaperpress.com/ptlens/

I've got some ideas about how to handle stabilizing it, but I'd like to test them out a bit before I recommend them. If I get some time once I get home tonight or tomorrow I'll post them.
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