Sensor size and FOV with relation to lens focal length?

[TeriyakiSandals]

MOST action cam use a 1/2.3" sensor. Combined with standard fisheye lens results in a FOV of about 120* horizontal / 170* diagonal.

However as the industry moves to smaller form factors like RunCam, Session, etc, a lot of cameras are moving toward using a smaller sensor size 1/3.2". Now obviously to achieve the same FOV they have a different focal length lens.

Does anyone has a calculator to see what focal lengths are using with 1/3.2" sensor size for a given FOV? Or what FOV we can expect taking a lens designed for a 1/2.3" sensor and mating it to the smaller sensor?

Thanks.

[nutsey]

In order to get effective focal length you need to multiply the lens f in mm by the sensor crop factor. FOVs are not that easy to calculate as we're talking about high-distortion fish-eye lenses...

[TeriyakiSandals]

In order to get effective focal length you need to multiply the lens f in mm by the sensor crop factor. FOVs are not that easy to calculate as we're talking about high-distortion fish-eye lenses...

would it be bigger or smaller for a bigger or smaller sensor? or does lens mount change too, holding the lens at a different distance from the sensor?

[nutsey]

The crop factor increases for smaller sensors.