Matchmoving software with the HPX 3700 (or HVX??)

Panasonic Cameras

Matchmoving software with the HPX 3700 (or HVX??)

Posted by Scott Smith on December 13, 2011 at 7:35 pm

Hi,

I’ve got some questions. I’m matchmoving and I was given these specs by the cameraman:

Scene 1
Start position 1:
90 inch lens height
204 inches away from subject
F4
7.6mm lens

End Position 1:
64 inch lens height
150 inches away from subject
F4
7.6mm lens

Someone told me that 7.6 is the focal length but it looks wrong. I think not having the correct information is affecting my tracking. Besides, if 7.6 is the focal length, wouldn’t it need to be multiplied by the crop value? 7.6mm seems really short.

I’ve also plugged in that the 2/3 chip is 8.6mm width and 6.6mm height.

I hope someone can help clarify the situation as I’m getting close in the tracking but not great.

Thanks,

spiral

David Coleman replied 14 years, 4 months ago 4 Members · 5 Replies
5 Replies

John Mastrogiacomo
December 14, 2011 at 9:09 am

According to Wikipedia:
https://en.wikipedia.org/wiki/Image_sensor_format#Table_of_sensor_sizes

The 2/3″ sensor size is 8.8mm x 6.6mm

You are never going to get exact measurements that work perfectly. You just have to experiment to get the best results.

John Mastrogiacomo
Spectra Video
Scott Smith
December 15, 2011 at 9:09 pm

hi,

Thanks for the answer. The thing is that 7.6 mm is very short for a focal length. Someone had mentioned that you have to multiply the focal length with the crop which is 3.93 and would give the focal length more around 28ish in focal length. Does this sound correct?

Also, the video camera in matchmover is squishing to 4:3, which is affecting the track as well, I think. Anyone know how to get that not to happen? The 2D view is 16:9 but when I solve for the camera it turns to 4:3 even though the camera options were correct anyways.
Jim Wilcox
December 15, 2011 at 9:50 pm

Depends on the original file format that the shot was captured with as well. If DVCProHD its PAR is going to be 1.33 (for 720) or 1.5 (1080) so perhaps the MM software you are using is not picking up on that.
John Mastrogiacomo
December 17, 2011 at 6:01 am

[Scott Rinehart] “The thing is that 7.6 mm is very short for a focal length. Someone had mentioned that you have to multiply the focal length with the crop which is 3.93 and would give the focal length more around 28ish in focal length.”

7.6mm on a 2/3″ camera at 204 inches is very wide. What is the shot?

John Mastrogiacomo
Spectra Video
David Coleman
December 27, 2011 at 10:04 pm

7.6 is a realistic focal length. 4.5 is super wide, but not yet fish-eye.

HPX3700, HPX2000, HVX200

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