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Why does smaller f-number imply greater aperture diameter and consequently, greater amount of light entering the lens of a camera?
As evidenced from my study across a number of resources, an absolute statement is:
A smaller f-number means greater amount of light being allowed in, and vice-versa.
The f-number is, after all, the ratio of a lens's focal length to the diameter of the aperture. Now, if the aperture diameter is kept constant and the focal length is just decreased, that would, in turn, reduce the f-number too.
Yet, in this case, the lens's f-number is reduced, which as per theory, should allow greater amount of light into the system (as evidenced by all theory I've read stating that smaller f-numbers mean greater light being allowed in).
But, ultimately, I believe the amount of light being let in is controlled by the diameter of the lens aperture that does remain constant.
Can someone explain this concept to me?