Axes Camera View Angle Behavoir

I want to be able to calculate exactly what part of my plots the camera can actually see. To do this I need a very good idea of what the camera view angle is. I have found this graphic

https://www.mathworks.com/help/matlab/creating_plots/defining-scenes-with-camera-graphics.html

Here it appears that the camera view angle is only top to bottom, Is this true? and if so can I calculate what the camera view angle from Left to right would be like this:

camva_left_right = camva(ax).*(Number_of_Pixels_Left_Right./Number_of_Pixels_Up_Down)

This seems inititive, but I'm not 100% sure that this is how this would work. This is also a very hard hypothisis to test, because my math right now relies on a vew estimates that are going to take some time to test.