When it comes to photography, a prime lens and a zoom lens are both essential. While there are some differences between prime and zoom lenses, they both serve the same purpose: taking clear photos with minimal distortion. A good understanding of the differences can help you decide which one is right for your photography needs. In this article, we’ll discuss the critical differences between prime lenses and zoom lenses.
Zoom lenses are an essential tool for filmmaking in general but even more critical for multicamera cinematography. With the ability to quickly reframe, change focal lengths, and maintain sharp focus, zooms become invaluable for achieving the shot under challenging conditions. Many cinematographers utilize zooms for various productions, from films to television to broadcast.
So, what is the difference between a zoom and a prime? First and foremost, it’s the difference between a fixed focal length (primes) and a variable focal length (zoom). Focal lengths are magnifications, much like magnifications for a microscope. The longer the focal length, the closer you feel to a distant object. The wider the focal length, the lesser the magnification, which results in things in the distance feeling further away.
In these cases, the “object” is relative. A person’s eye can be a distant object if they are only seven feet away from the camera. With an appropriate telephoto focal length, we can get a tight shot of just the eye. Zoom lenses can render both extremes and all the in-between magnifications with the turn of the zoom ring.
This ability comes at a cost, which is reflected in the fact that zoom lenses are typically larger, heavier, and have slower T-stops. This is due to the complexity of the optical design and mechanics. Modern zoom lenses do a great job of covering an extensive focal range while performing relatively well compared to older lenses. Primes typically offer a cleaner, more precise look, especially when wide open. Since primes are generally faster than zooms, you can achieve a shallower depth of field with smaller T-stops (larger IRIS opening). These are why primes are preferred for creative purposes, while zooms are seen as more practical.
Optical Design. Zooms typically have many glass elements in their designs, where two or more groups of elements are variable and moving while zooming or focusing the lens. Zoom designs are more complex than fixed focal length lenses (primes). The designer must decide what compromises will be made and what is an acceptable level of distortion, chromatic aberration and exposure fall off from the center of the frame to the edge.
Mechanics. Since several glass elements in a zoom lens must shift when the focal length changes, the mechanics must be precise and repeatable. Well-designed cinema zooms will perform similarly even after a lot of time in the field. They are built with robust housings and well-lubricated moving parts, but the barrel designs are more complex than prime lenses, so servicing a zoom take more time and effort. Plus, more things can go wrong with the mechanics, which means zooms are more likely to require servicing after heavy use.
A good understanding of the differences between prime and zoom lenses will allow you to decide which lens is right for you.