This question torments a great deal of lens buyers- Should I purchase a zoom lens or a fixed prime lens? When it comes to versatility and convenience, zoom lenses deliver a wide range of focal lengths at the flick of your wrist; without having to constantly change lenses. Quickly enabling you to frame and capture a moment with the appropriate focal length. This is a advantage for zoom lenses but also their biggest weakness. Their is a compromise in image quality. Complex arrangements of large groups of elements inside the lens moving back and forth to enable the zoom, reduce the optical quality of your images.
Despite their versatility Zoom lenses can cause a several issues with your photography. The Sharpness of your images is the first victim, barrel and pin cushion distortions can often appear at the wide-angle and telephoto ends of your lens zoom range. Zoom lenses can also cause vignetting, a reduction of an image’s brightness or saturation. You can also expect an increase in chromatic aberration (known as colour fringing around high-contrast edges in a scene). This effect is most commonly seen when you’re using large apertures at the wide-angle end. Zoom lenses are also more susceptible to ghosting and flare.
If you choose a high-quality prime lens, distortion and vignetting will be much less noticeable. Their are fewer moving parts; prime lenses are optimised to a specific focal length or purpose. Which means optical performance is generally better and lenses an be made with larger apertures. The Sharpness of your images will also be unparalleled, so you can really make the most of the high-resolution sensors fitted to current digital cameras.
Another advantage of using prime lenses is that they’re generally ‘faster’. Which means they have a larger maximum aperture, which enables faster shutter speeds. For example, a typical 18-55mm zoom lens has a maximum aperture of roughly f/4 at the wide-angle end, shrinking to a mere f/5.6 at about 50mm. If you Switch to a 50mm f/1.4 prime lens the largest available aperture is four stops faster. In low light you’d be limited to a shutter speed of, say, 1/15 sec with a typical zoom (unless you increase your ISO setting). However, an f/1.4 lens will enable a much faster shutter speed of 1/250 sec. An f/1.8 lens is 3.3 stops faster than an f/5.6 lens, and even an f/2.8 model is two stops faster.