I think I understand the relationship between the three, but I would like some feedback. I still am fairly unsure about lens speed and is what I'm mostly interested in. From my understanding: Aperture is the total diameter of the lens and numerical aperture is the ratio between the aperture and focus length. The numerical aperture tells the maximum angle a light cone from and object a specific distance can handle while allowing all the light to pass through the lens. Is the speed of the lens simply the aperture without any type of shutter?