These days, when you buy a camera you’ll often get a zoom lens bundled with it. You might even get two. And whether they came with the camera or not, most photographers use zooms all the time, because they’re convenient and flexible.
So why would you want to switch from a zoom lens – one where you can change the focal length – to a prime lens – where the focal length is fixed? There are actually lots of reasons. And we’ve outlined are 7 of them below.
In the greater scheme of things, zoom lenses are actually a pretty recent luxury for photographers – if you got into photography in the last century – yes, there are still people around who did that – you probably started out on a prime lens, like a 50mm or 35mm model. Ownership of zooms was far less common, and in fact, having one with a ‘fast’ maximum aperture – one that doesn’t get smaller as you extend the focal length – is actually an even more recent phenomenon. Although they’re now comparatively common, affordable ‘fast’ zoom lenses like Sigma’s 18–50mm f/2.8 EX DC Macro didn’t arrive until the mid 2000s, when they blew everyone’s head back.
So let’s look at some of the reasons why modern photographers would want to switch from zooms to primes…
1/ More light, more choices
Prime lenses almost always feature wider maximum apertures than zooms – that’s the aperture value that’s written in the lens’s name. And a wider maximum aperture means more light can be recorded by your camera’s sensor in the same amount of time as a smaller one. More light means you get advantages like faster available shutter speeds (hence the term ‘faster’), or to use lower ISO settings while making a good exposure. For instance, if you’re using the long end of an 18-55mm f/3.5-5.6 lens, and switch to using a 50mm f/1.8 lens at its maximum, you’ll get a 3 and 1/3 stop advantage, equating to a shutter speed increase from 1/15sec to 1/160sec. What this often means is the ability to shoot with better quality in low-light conditions, or freeze the motion of moving subjects.
2/ Improved AF performance
The extra light you get from the wider aperture of a prime lens also means improved autofocus performance. That’s because AF is normally performed with the lens’s aperture in its widest position. Now, not all lenses have the same AF speed and response, but if you put a slow zoom and a fast prime with similar AF characteristics together you’ll get faster and more accurate AF speed with the latter.
A faster aperture also means it’s easier to add teleconverters to prime lenses. The AF sensors on a camera are rated by f/numbers, and if you have a really good body you might get something like f/8 for those points at the centre of the frame. Add teleconverters to a slow zoom and the maximum aperture will soon get past this point, wherein the lens may need to be manually focused.
3/ Better bokeh
Here’s where most photographers will sit up and take notice. The very wide apertures offered by many prime lenses also give you access to very shallow depth-of-field effects. These are instrumental for separating the subject from their background, and make for far more pleasing portrait and action shots than those shot with a greater depth-of-field.
But there are drawbacks to this – in bright light, to use the widest apertures and therefore get that ultra-shallow depth-of-field you’ll most likely need to fit a neutral density filter, cutting the amount of light, and allowing you to shoot without over exposing the image.
4/ Smaller and lighter lenses
Okay, maybe it’s not fair to say primes are always smaller and lighter than zooms – because they’re not! But comparatively, you can expect a 200mm f/2.8 to be smaller and lighter than a 70-200mm f/2.8. Sure you lose the zoom’s flexibility, but how much this matters depends on the subjects you’re photographing and how you’re shooting them.
There are plenty of examples of small, light prime lenses, including Nikon’s 300mm f/4 PF – an optic that supplies incredible range and quality for its size and weight. Pick up a 50mm f/1.8 lens and you’ll be amazed by the quality from a lens that only weighs 160g.
5/ Increased image quality
Again, that’s ‘usually’. You can still find low-quality primes, but comparatively, fixed focal length lenses will outstrip zooms in the vast majority of cases. Most of the time this is down to construction. The multiple moving elements of zoom lenses make it very difficult to keep image quality close to perfection, and you’ll often find a dip in sharpness at one end of the zoom or the other. Primes, being simpler in design, will generally suffer fewer distortions and aberrations, too, so expect to see increased sharpness, less bowing of straight lines, or coloured fringing degrading image quality. Of course, primes aren’t perfect and most aren’t at their best at the very maximum apertures, but neither are zooms!
6/ Work harder on your compositions
Primes lenses won’t make you a better photographer overnight. In fact, if you’re moving from a zoom to a prime, the lack of options can feel restrictive and challenging to start with – but that’s a good thing. Sticking to single focal lengths will help you get to know how they work and therefore what’s best for your subject. Take a prime lens out and keep using it alone and you’ll start to ‘think’ in that focal length, seeing more opportunities and getting better shots than the scattergun approach of zooming in and out can get you. Keep working with the same focal lengths and you’ll also get a less random and more consistent look to your work as a collection.
7/ And they don’t need to cost a lot
In terms of bang-for-your-buck, prime lenses can have a massive impact on your photography. You don’t need to spend thousands to see the effect, and the most obvious example is in 50mm lenses – the Canon EF 50mm f/1.8 STM or Sony DT 50mm f/1.8 SAM can revolutionise a photographer’s work for less than £150. If you’re into landscapes a 20mm or 24mm f/1.8 will see you well for low-light scenes and starry skies, and Nikon’s AF-S NIKKOR 24mm f/1.8G ED is a snip at just over £550.
Prime lenses should be seen as an investment, too. Get a good one and you’ll keep it longer than your camera body!
DigitalRev 