# Sensor size of Sony HDR-HC7e

I want to motion track a shot from my Sony HDR-HC7e camcorder and I am not quite sure about the horizontal sensor size(width). I set the focal length to minimum and the recording to HDV 16:9

This manual (HC7e and HC7 are basically the same) states it is a 1/2.9" sensor with a diagonal of 6.3mm (page 101). But if I do my calculations and multiply (1/2.9) with 25.4 to convert it to mm I get 8.75862069?

The camcorder outputs a 1440*1080 interlaced .m2t file. The image in this file is squeezed by a factor of 1.33. as seen in this example. So I suppose that the sensor has an aspect ratio of 4/3(1.33) So I did some math:

$$a^2 = b^2 +c^2$$

$$\begin{matrix} a_1 &=& 6.3\\ a_2 &=& 8.75862069\\ b &=& x\\ c &=& 1.33x\\ \end{matrix}$$

$$6.3^2 = x^2 + (1.33x)^2$$

$$\begin{matrix} x &=& 3.78605\\ 1.33x &=& 5.0354465\\ \textrm{horizontal 1} &=& 5.0354465 \end{matrix}$$

$$8.75862069^2 = x^2 + (1.33x)^2$$

$$\begin{matrix} x &=& 5.26359\\ 1.33x &=& 7.0005747\\ \textrm{horizontal 2} &=& 7.0005747\\ \end{matrix}$$

So I thought because there always is a relation between sensor size and focal length, I just take the sensor size horizontal 35mm and the corresponding 35mm focal length equivalent of 49mm (manual page 101) and get the ration: 35 / 49 = 0.714285714 then multiply the true focal length of 5.4mm by that and get a horizontal sensor size of 3.857142856

So now I have got 3 possible horizontal sensor sizes. Now I want to calibrate my lens with a set of images like the linked one. Should I leave them with the 1.33 aspect ratio and where would I specify that in the OpenCV camera calibration or do I unsqueze them and then calibrate? And do I even need the sensor size and focal length for OpenCV camera calibration?

• You might have a better time asking about this on Photography(photo.stackexchange.com), I'd guess they will know more about camera sensor geometry. This is a bit out of our bailiwick here at CGSE. Sep 22, 2020 at 17:51
• Jup just dit, thanks fo the hin. Sep 22, 2020 at 18:44