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I'm trying to compute the focal length for different field of views of a camera.

Therefore I need the sensor size horizontally and vertically, but in the datasheet I only have the following information: 1/3" 2.4 MP image sensor. The image size is 1920x1080 if that's needed.

How do I get the size of the sensor?

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It is not possible to calculate the sensor size with that information because the 1/3" measurement refers to the diameter of a hypothetical tube that would enclose the sensor. That sets a limit on the diagonal of the sensor but it not an exact fit.

The the sure way to know the sensor-size is to measure it or find the part number and look at specifications of that particular sensor from the manufacturer.

There are common approximations and Wikipedia has 4.8 x 3.6mm for a 1/3" sensor with 4:3 aspect-ratio but you will need to figure out if that matches your sensor and what region was cropped to get the 16:9 aspect-ratio of your images. Sometimes, only the vertical dimension is cropped but sometimes both, effectively creating an equivalent of a smaller sensor. There are native 16:9 aspect-ratio sensors too, and they can fit into 1/3" but that could be wider than 4.8mm.

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  • I dont't have this information, but I know the resulting image is 1920x1080, which is 16:9. Could I use this aspect ratio to compute the actual size, or is it still possible that the actual sensor has a 4:3 aspect ratio? – gab Apr 15 at 8:54
  • Unfortunately, you can't tell that is a 16:9 aspect-ratio image from a 16:9 sensor or from a larger sensor cropped to 16:9. Both are quite likely. If it is taken by a camera designed for photography, then the sensor is likely to be either 4:3 or 3:2 but there are many other ratios possible. If the output is from a video camera, including surveillance/security ones, then 16:9 would be more likely but not guaranteed. Phones are even more diverse, in terms of aspect-ratio but also how they crop which varies to simulate different focal-lengths. – Itai Apr 15 at 14:34
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I found this at the Digital Camera Database

Another list is at the Wikipedia article for Image sensor format

Which both say for 1/3": 4.8 x 3.6 mm

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