camera set up for go pro inside max

[stevesideas]

I'm having to match a gopro camera inside 3dsmax but I'm not sure things are quite right. I have been told that the lens is equivalent to 21mm (medium FOV) which in max becomes 81.2026 FOV (horizontal). I am using 1920x1080 (16.9) format. Based on this chart: https://gopro.com/support/articles/h...ov-information I cannot see any value that even comes close to the 81.2026 FOV that max equates to. Does anyone know what I am doing wrong ?

[pokoy]

Did you set the sensor size to match the go pro? According to this site (https://gopro.com/support/articles/hero3-faqs) the sensor varies depending on the model. Also, it seems the ratio is 4:3, not 16:9 which will result in a different diagonal FOV. Once you set your image ratio to 4:3, use the correct sensor size and match the horizontal FOV of the camera you should have a matching setup.

[Dave_Wortley]

You'll probably need to print off your own distortion grid, take a photo/film with your GoPro then you can use the VRay Lens analyser to make a profile for the GoPro and then you can load this lens distortion profile into the Vray Camera and set your FOV to 170 or whatever the GoPro comes out as.

Be interesting to see it if you don't mind sharing?

GoPros shooting 4:3 or 16:9 depending on your settings, I would do the distortion test at 4:3 and then you can just change your render size to 16:9

[Vizioen]

Would be great if you would post your findings here too, because I have a feeling I will need this information the coming year.

[Ihno]

Hi,

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

And i also have a problem with 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/h...ov-information

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

On the other hand this page:https://gopro.com/support/articles/c...ictures-videos

Tells the fov is whide:170 medium:127 narrow:90 but none of these values are 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 the gopro pages show´s 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 it has a width of 5,371mm.
Sensor sizes list: http://www.dpreview.com/glossary/cam...m/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.
Didn´t use the lens analyse tool until now. But i´ll try it.

[stevesideas]

Sorry for the late response. I was given a shot directly from the go pro camera to match within 3dsmax. Normally I would un-distort the image first but for this job I can get away with not doing that.

[Ihno]

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/c...ictures-videos

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/h...ov-information

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

In this 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 thing 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.

[Dave_Wortley]

I just grabbed a goPro photo off the web ran it through the vray lens analyser and created a profile, not sure which goPro it was from. You can do this properly and it'll work out correct for you.

Open the Vray Lens Anaylser, print off a test chart, take a photo of the test chart filling as much of the frame as possible and try to make it fairly straight to camera. Try automatically detecting the grid if not draw your own lines out and the analysers will probably figure it out. You should be able to undistort your goPro image with your profile. Export your lens profile.

Create a Vray Camera with a 14mm focal length and load in the Vray lens profile you just made into the distortion. You'll need to be using VRayRT to see the distortion in action, it won't work in the viewport.

I've attached mine, made from just some image I downloaded from the web, I think it's just the goPro HD original, so you're best off doing it again with your camera.

GoPro.zip