How Focal Length Can Dramatically Change Portraits - Digital Photo
Focal Length of a Lens
The value of the focal length of the lens is equal to the value of the image distance when rays are (A) Passing through optical center(B) Parallel to the principal axis.(C) Passing
Filmmaking Test: How Format Size Affects Your Focal Length | B&H eXplora
What is Focal Length in Photography? - Focal Length Explained