Zoom and prime lenses in photography!
A zoom lens can operate across different focal lengths. An example of a zoom lens is a 24-70mm. This lens can shoot at both wide (towards the 24mm side) and normal (towards the 70mm side) focal lengths.
A prime lens shoots at only one focal length. Also called a fixed focal length.
An example of a prime Lens: A 50mm lens.
There is no zooming!
Maximum aperture is the widest aperture a lenses is able to shoot at.
Zoom Lenses with Variable Maximum Apertures
A zoom lens that operates over different focal lengths and different maximum apertures is called a variable lens.
Example: An 18-55mm f/3.5-5.6 lens. A common kit lens available with many entry-level cameras. The max aperture at 18mm is 3.5, and the maximum aperture at 55mm is 5.6. Meaning you can only shoot with f/3.5 at 18mm. Once you start zooming, your max aperture changes!
Zoom Lenses with A Fixed Maximum Aperture
A zoom lens that maintains the same maximum aperture over its entire focal range has a fixed maximum aperture.
Example: A 24-70mm f/2.8 lens. Meaning that the maximum aperture at 24mm is 2.8 & the maximum aperture at 70mm is also 2.8.
A fixed maximum aperture is an important feature for professional photographers. They can keep their f/2.8 over the entire focal range. This maintains the same depth of field no matter where they are zooming.
Different Price Points
Walk into a camera store and you will notice that fixed aperture zoom lenses are more expensive than variable aperture lenses.
Here’s why: Simply put, the reason is its design. More lens elements, more glass, more hardware, and more complex engineering. All of this means higher production costs and a higher price tag for photographers!