CGTalk - Estimating focal length for matchmoving?

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dax3d

07-21-2003, 02:02 AM

Hi,

I was wondering if anyone had any tips for estimating focal length. I have some footage where I could not get measurements, and was curious how people went about this. Is this a complete trial-and-error thing? Or something you get better at with experience.

thanks for any feedback

alexgk

07-10-2004, 03:59 AM

hi, I just did a search and saw your post. I also was curious about this. Did you ever find out any good info?

WhiteRabbitObj

07-10-2004, 08:02 AM

Dude, Alex, that post is a year old. Lol.

Your best bet about this would be to construct geometry for the scene to the best measurements you have, match is as close as possible by eye (translative matching) and then from there, adjust your lens. Mostly you'll just eyeball it. A lot of times you can guess that it's a 35mm or a 10mm or 100mm or somewhere close, etc. The guy I learned tracking from could guess then lens data from a shot pretty accuratly. Of course, he does it for a living so you get used to the look of a lens pretty quick I guess.

You should be able to look up the lens info though based solely upon what camera you used. If you know what type of camera it was, you can then look up the lens info in the documentation.

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