F900 Sensor dimensions
Posted 23 November 2006 - 06:26 PM
Posted 23 November 2006 - 06:59 PM
I'm doing some tracking on material originating on the F900 and one of the things I can enter is the "Film Back" size of the camera. The default values aren't correct as it isn't taking account the sensor size in the calculations. I wanted to ask anyone out there if they could provide the measurement in mm of the film equivalent of the film back size. I assume it's the active sensor area of the 16x9 aspect 2/3 inch chip but I have a feeling that it isn't that simple as using 2/3" converted to mm. Can anyone provide numbers that people can agree upon?
I found these dimensions - 9.58 mm x 5.39 mm, but my schoolboy maths would make the diagonal of that somewhat less that 2/3 inch.
I believe that if you did find the accurate measurements of the sensor area, this wouldn't necessarily help your tracking as such. What it would do is more accurately calculate the focal length of the target. I have come across examples before where the film back parameters are researched and added without fixing issues.
The most likely culprit is pixel aspect ratio. Note this is different to picture aspect ratio. Your 1920 x 1080 image has an aspect ratio of 1.77:1, but your pixel aspect ratio is 1:1 (because there are more of them horizontally).
Having said that, there is also this possibility. If the recording from the F900 was made to HD-CAM AND you are working on a post platform that does not decode the HD-CAM data back to the target HD format, then you might be working at a resolution of 1440 x 1080 (the native resolution of HD CAM). In this case your pixel aspect ratio is 1.33:1
Baraka Post Production
Posted 24 November 2006 - 05:40 AM
Since I'm tracking a Targa sequence that is 1920x1080 square pixels, those other issues shouldn't be a factor. I've already got a set of numbers to use when working with Varicam originated footage, and I'll cross check it with the numbers you provided.
I would love it if we could compile a table of "film back" / active sensor sizes for various HD acquisition cameras for tracking purposes in post. These numbers tend to be hard to come by as opposed to film.
Edited by Albert Cheng, 24 November 2006 - 05:43 AM.