Getting hold of camera sensor sizes (or film backs) for matchmove / camera tracking purposes is not always straightforward. This is in part because there is a lot of misinformation on the internet, but also because of confusion over physical sensor size, effective sensor size and any cropping based on the chosen format.
The table below should provide accurate numbers (as of Jun 2013) for a number of popular cameras. The key figure is the pixel size. This can be multiplied by the capture resolution format to give an accurate filmback size for tracking purposes.
Sensor Sizes
The sensor sizes given are for the largest formats. So if you were dealing with 4K footage shot on a RED EPIC MYSTERIUM X you would multiply the pixel size by the format (4096 x 2160) to give you the effective sensor size/film back of 22.12 x 11.66mm.
Ars Visualis 
so using this division by the pixel size, your saying that if I put on a 32mm lens and then change down to a smaller resolution I’ll be changing the field of view that I can expect of that lens?
It depends a little on the camera. Where the camera actually reduces resolution by using a smaller portion of the sensor then yes. So for example on an Epic camera you would see a change in the FOV as you change the resolution. However, some cameras still use the full sensor but downscale the captured image to produce a lower resolution (e.g. the Blackmagic camera uses the same sensor size for 4K and HD capture it just downscales the captured data to record HD).
Where do you get that Pixel Size (mm) value from? I’m trying to find that info about the Sony f-55 with image format 4096×2160.
The pixel size (mm) you have listed is 0.0059 but how do you get that value? Or where on the Sony website is it listed please? I cannot find it anywhere online or in the manual.
Thanks
Hi Nicole – the pixel size is derived from the effective sensor size and the maximum resolution that can be captured (in the case of the F55 – 4096 x 2160). The figures were pulled from the pro.sony.com web site, although it was a while back so I don’t have a direct link to give you (and it is not easy to find). You’ll find similar calculations here http://www.fdtimes.com/2013/12/27/sony-firmware-3-0-update-16mm-mode/ Unfortunately this information is very hard to track down accurately, which is why I posted my calculations for my own benefit online. I hope this helps.