I need to purchase my first ever lens. So far I've only used lenses that were built into a camera. This specific lens is for the BlackMagic Deign Pocket Cinema Camera (a video only camera, but one that uses photography lenses). I would prefer this to be a prime lens.
I have tried to find the exact way to calculate the focal length of the lens I need but I have not been able to find a good resource to make this simple enough for my limited optics knowledge. Can you please explain a simple way to calculate the focal length of a lens given the following inputs as an example:
I would prefer a simplified mathematical explanation so that I may use it to make similar determinations in the future using a "plug and chug" method.
I have found this answer. Using that method, I came up with:
Required lens focal length = 7.02mm sensor height x (77in / 36in) = 15mm
Is that correct?