Prime Lenses

A prime lens is a lens that has a single, fixed focal length, as opposed to a range of focal lengths like a zoom lens. For example, many photographers like to use a 50mm lens as a good general-purpose lens. Street photographers often favor a 35mm lens as it allows them a wider view. Portrait photographers often use an 85mm lens which is flattering to the human face. While there are a number of advantages to prime lenses, the downside is that you have to physically move yourself closer to, or further from your subject in order to reframe your shot. Many people prefer to use zoom lenses because they are useful in a wide variety of scenarios.

The advantages of a prime lens

There are a couple of significant advantages to using a prime lenses. First of all, prime lenses typically deliver much sharper, clearer images than comparable zoom lenses. The reason for this improved performance is simply that prime lenses contain fewer glass elements than zoom lenses. Every glass element has an effect on the light passing through it, and so the less elements the better. For example, the Nikon AF-S Nikkor 50mm f/1.8G lens contains just 7 elements, whereas the AF-S DX Nikkor 18-200mm f/3.5-5.6G lens contains 16 elements. And indeed, the sharpness score for the 50mm lens is much higher, while distortion and chromatic aberration scores are lower.

Prime lenses have wider maximum apertures

The second major advantage of a prime lens over a zoom lens is that a prime lens usually has a much wider maximum aperture than a comparable zoom lens. Looking at the Nikkor lenses mentioned above, you can see that the 50mm has a maximum aperture of f/1.8. The 18-200mm lens has a maximum aperture between f/3.5 and f/5.6. The significance of a larger maximum aperture is two-fold. Firstly, it gives you improved low-light performance, as that wider aperture essentially allows more light into the camera. Secondly, it allows you to create the so-called ‘bokeh effect’ which blurs out the background in your images and makes your subject really pop.

Prime lenses and the bokeh effect

The bokeh effect is actually caused by a shallow depth-of-field—a narrowing of the space within which things are sharp and in focus. The bokeh effect is probably the number one reason that photographers choose to use prime lenses. Portrait and wedding photographers in particular love the artistic quality that a shallow depth of field provides, and so they regularly choose prime lenses as their go-to. The downside of using a shallow depth of field is that the images are usually less sharp than those taken at narrower apertures. Also, it can be more difficult to nail your focus when the depth of field is narrow so you might find that you get less usable shots overall from your shoot.