Physical camera gopro settings. And FOV confusion

[Ihno]

Hi,

I’m trying to figure out how to setup the Physical camera to match a gopro Hero3 Silver (medium fov).

One big and confusing problem is the fov.
I don’t know witch kind of fov the Physical camera wants... Horizontal? Vertical? Diagonal?

On this Page: https://gopro.com/support/articles/hero3-field-of-view-fov-information

gopro tells witch h/v/d fov the hero 3 has.

On the other hand this page:https://gopro.com/support/articles/curved-nature-pictures-videos

Tells the fov is w170 m127 n90 but these values are not in the list of the first page...

To get a value for the distortion I made a picture of a dot grid in a distance of 21cm. (the distance was a necessary because I could only print the grid in a3 and wanted to fill the picture with it)
after that i rebuild the setting in 3ds max.
None of the fov´s gopro´s pages show matches the view I get from the real camera. Most of them are too big, the plane with the dot grid picture doesn’t fills the entire view. I had to set it to 82.8

After that I thought I could do it with the focal length… The page with the fov list also tells the medium setting´s fov equivalent would be 21mm. The gopro hero3 silver has a 1/2,7" sensor whereby a width of 5,371mm.
Sensor sizes list: http://www.dpreview.com/glossary/camera-system/sensor-sizes

If i set the sensor size to 5,371mm and the focal length to 21mm I get a very low fov witch is way to small...

I’m totally confused.

The distortion is another issue there are no cubic distortion values for it on the internet. And i don’t trust the value I figured out (0.095) as long as I’m not Shure about the fov.

Presets for the Physical camera would be so nice!!!

[Ihno · Accepted solution]

After taking a photo and matching it roughly i have some ideas what values the gopro page gives.

The following depends on a gopro hero3 in the medium mode.

First the FOV:

On the other hand this page: https://gopro.com/support/articles/hero3-field-of-view-fov-information

Tells the fov is whide:170 medium:127 narrow:90 but none of these values are in the list of the first page...

I dont know how they come to 127° for me this seems to be a lie.

On this Page:https://gopro.com/support/articles/curved-nature-pictures-videos

gopro tells witch h/v/d fov the hero 3 has.

On that list they say:
16 x 9 M: Vertical55 Horizontal94,4 Diagonal107,1

I played with the settings and allways a fov around 88 seemed to be proper.
I think the physical cameras FOV is horizontal and gopro considers the distorsion witch makes the picture a bit bigger. I think they do this just because it sounds better.
The FOV of the physical camera on the other hand don´t consider the distorsion in the fov. This is why its 88 instead of 94,4.

Focal Length:

This is funny. After i find a proper FOV i was wondering about the focal length max calculates out of this.
I set the sensor size to 5,371mm witch is the right size of the sensor.
Max calculates a focal length of 3,154mm this poles apart from the 21mm they declare.
Then i set the sensor size to 35mm (full frame) aaand voila the focal length max calculates based on the fov and the sensor size jumps to 21.

The 21mm they consider would be proper if the sensor would be a full frame sensor. In fact the real focal length is 3,154mm.
And in this case they seem to exclude the distorsion form there calculations.