August 23, 2013, 04:03:56 pm
We created Lumion so the focal length corresponds with 35mm full frame. This makes it easier to look up the desired focal lengths.
A focal length which comes close to the human eye is about 50mm.
This is just a common value and I'm not sure this is an exact scientific value. Well actually I'm pretty sure it's not. It's probably what people commonly accept as a good value.
For a more scientific approach there are many things involved. For example: what aspect of the human eye are you trying to match with the camera lens?
- Perspective distortion
- Field of view
For each there are multiple ways to approach this issue. If you want the same field of view you have to take into account that the effective field of view is bigger for two eyes for example.
There are many other ways you can look at this and my opinion is that probably the best way to approach this is to use common wisdom. Use a 50mm focal length and when you need a bit more field of view you could go to 43mm to get a wider area.
As I remember the 50mm in Lumion is comparable to a 16:9 cutout of a full frame 35mm image. When you use a 41mm focal length you effectively have a vertical FOV which is similar to the horizontal FOV at 50mm.
You can look at it like this: Normally in a 35mm camera the lens projects on a square area. In this square area you get a field of view of about 39.6 degrees. The top and bottom are then cut off to get the 16:9 Aspect ration. This means that the horizontal FOV is still 39.6 degrees.
If you look at the chart on this page:http://en.wikipedia.org/wiki/Angle_of_view#Common_lens_angles_of_view
you can see that at 50mm the horizonal FOV is 39.6 degrees. This is the same as in Lumion! The vertical FOV is a bit different but that's because the chart uses a 3:2 aspect ratio and Lumion uses 16:9. Don't get confused by the aspect ratio. Simply concentrate on the horzontal FOV. This FOV is exactly the same as a full frame 35mm camera.
At the same chart is says:
"For comparison, the human eye has an angle of view of about 160Â° by 75Â°."
This would translate to a focal length between 2 and 12. This would give you the same FOV as the human eye but would also introduce a huge amount of perspective distortion. Therefore it's better to stick to 50mm. The reason this is possible is because the eye is different than a a camera. The camera projects on a flat plane while the back of the eye is curved. This combined with the fact that you have two eyes results in a perspective distortion of about 50mm lens with the field of view of a 12mm lens.