January 18, 2012, 05:54:02 pm
Thank you Remko for your detailed answer!
Hmm I did some more testing and looking on the internet and as it seems we DO use the right formula's.
If you look at this calculator you can see that for a 50mm focal length the 35mm film equivalent horizontal fov is exacly 39.6 degrees. This matches with the angles I get in Lumion.
We then crop the top and bottom to get a 16:9 image. So, as it turns out we did have it right the first time. No worries! Everything will stay as it is!http://www.frankvanderpol.nl/fov_pan_calc.htm
All the cunfusion comes from the fact that there are many places where we can find the conversion between focal length and field of view but they do not explain which field of view is meant. The diagonal of the uncropped image would seem the most logical angle to me but as it turns out it's the uncropped size (horizontal or vertical) of the image.
This calculator for example uses the diagonal: http://kmp.bdimitrov.de/technology/fov.html
Which explains the difference with the fisrt calculator (note that they also show the diagonal fov in the first calculator)