Lens conversion from landscape to portrait.

[cg_Butler]

Hi all.

 

Does anyone know the lens conversion from landscape to portrait on a camera? There must be some maths involved, or a table somewhere.

 

I'm doing some photo montages and the photographer took all the images in a portrait fashion. From my past experiences this is fine. You just have to add more to the side of the photographs to make it a landscape ratio and match to that.

 

I am using 3dsmax's built in camera match utility which works perfectly. But i then have to adjust the lens on the camera to make the geometry fit back over the top of the photograph.

 

I wondered if anyone knows the exact maths involved, so i know with confidence that's can just type in the correct lens fov on the camera that is created and it will give me an accurate match.

 

For example.....

 

If I use a fixed lens of 14mm on a full frame 35mm DSLR. In portrait mode, I know my 3d camera should have a 14mm lens. But in portrait mode it is something else. I have tweaked my camera to have a 9.4mm lens and it all fits nicely. But I'd prefer a higher degree of accuracy.

 

Thanks in advance.

[RyderSK]

I switch the "horizontal" mode to "vertical" next to FOV field, then input the same FOV value. Horizontal 14 (equal to 104.25 degrees) gave me 10.5 in vertical. I am not sure how close this is being the camera in Max generally being somehow inaccurate, but since I don't do photomontages much at all, this is all I used. In any case, you can always use it as a starting point.

[Stephen Thomas]

Camera aperture is circular, so orientation should be irrelevant. Horizontal FOV will change, but focal length is absolute. If the camera match facility doesn't allow for vertical photos then that causes a problem, admittedly. Go by sensor size, which is 36mm x 24mm. So, 14mm / 36 * 24 = 9.333mm in your case.

[Corey Beaulieu]

The math is (FOV) = 2*arctan(Sensor Dimenson / (2*focal Length))

 

The Sensor Dimension should be 24mm in your case and the Focal Length 14mm. FOV is then 81.203 degrees.

 

To be clear though, this is assuming your camera only reads a horizontal FOV value as a V-Ray Camera does. With a Standard Camera you will just have to leave the FOV at horizontal and type in the value, ignoring the Focal Length parameter.