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# Can anyone guess what the focal length of the lens would be from this film clip?

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 Can anyone guess what the focal length of the lens would be from this film clip? by Ed Zenonon Apr 17, 2012 at 12:07:26 am

When the camera is circling around Harrison Ford throughout the clip (starting at 0.41)? Any idea what the focal length could be? Also approx how far away would the camera be from subject?

I need the camera info for virtual cameras I'm using to model his head in 3d :)

 Re: Can anyone guess what the focal length of the lens would be from this film clip?on Apr 17, 2012 at 2:07:16 am

It's reasonable to assume it's shot on super35 since it was a big budget film. With that in mind, an 85mm lens gives a working distance of 6ft which is nice for a dolly. Alternately, a 100mm lens at 7'6" could be an alternative. Both have been calculated with pCam for iPhone.

Regardless, they're both guesses as there really isn't a good depth cue for subject/background and so on.

 Re: Can anyone guess what the focal length of the lens would be from this film clip?on Apr 17, 2012 at 2:31:49 am

Well, just looking at it, it's hard to say, as Angelo said... but applying a little logic...

Since it's not a specialty shot requiring a very specific arc, at some point someone probably yelled to grab curved dolly track off the truck. Chances are pretty good it was Matthews track since that's what you usually see on a big-budget "real" feature shoot. Their curved track comes in arcs that make circles with outside diameters of 10', 20', and something really big like 70' or so, if memory serves.

We can guess that that was the middle size. The arc is not nearly tight enough to be the 10' track, so it's probably the 20'. With the radius of 10' in that setup, accounting for the 24.5" width of the dolly, that would put the camera center (assuming it was centered on the dolly) at about 9' from the talent. The film plane would be about 8' from the subject. If that's the case, based on the framing of that shot I'd say you're looking at a 80mm lens.

So... my guess is 80mm at 8 feet from the subject.

Of course, that's a wild guess... the dolly move is so slow we can't tell if there was any panning that could actually vary the subject distance, and the focal length.

T2

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