Big Test
The modest maximum apertures offered by most zoom lenses can cramp your style. Matthew Richards presents his prime picks that go all the way to f/1.4
Sharp, fast and usually fairly lightweight: eight FX-format primes, all with a constant maximum aperture of f/1.4, are compared and rated in our group test
Top-quality zoom lenses often have a widest available aperture of f/2.8, which remains constant throughout the zoom range. The most favoured examples include the Nikon AF-S 24-70mm f/2.8G and the Nikon AF-S 70-200mm f/2.8G VR II. For DX SLRs, there’s also the AF-S DX 17-55mm f/2.8G. They’re all pro-quality optics with the kind of zoom range that we all love for the sake of versatility.
There are times, however, when you want something a bit faster. There’s a particularly ‘fast’ Sigma 18-35mm f/1.8 zoom lens for DX cameras but, generally speaking, if you want a wider aperture than f/2.8 you’ll need to switch to a prime lens. The Nikon AF-S 50mm f/1.8G is relatively inexpensive at £150/$215 and the older Nikon AF 50mm f/1.8 D-mount lens (with no internal autofocus motor) is even cheaper at £100/$110. Bearing in mind that most consumer-class zoom lenses are not constant-aperture, and offer a widest aperture of only f/5.6 at the long end of their zoom ranges, an f/1.8 lens is three-and-one-third stops faster. We’re raising the bar even higher for this test, focusing on f/1.4 lenses that are four stops faster. But why the need for speed?
So-called ‘faster’ lenses with larger available apertures naturally enable faster shutter speeds. In fact, in bright sunlight you may not even be able to use the widest available aperture of a fast lens as the camera won’t be able to deliver a sufficiently fast shutter speed to avoid overexposure. Fast lenses really come into their own when you need to shoot handheld in very dull lighting conditions, for example indoors or at twilight. At least, that used to be the case.
Nowadays, many Nikon zoom lenses have VR (Vibration Reduction), which offers as much as a four-stop benefit in beating camera shake. This largely negates the need for a faster lens, but only when shooting static subjects. While VR (and competing optical stabilisation systems in other makes of lenses) can fend off camera shake, it can’t do anything to counteract motion blur. If you need to freeze moving subjects, a faster lens that enables greater shutter speeds is an excellent remedy. Even here, though, recent and current Nikon SLRs deliver such good image quality at high sensitivity settings that you can often increase the ISO rather than fit a faster lens.
There’s still one scenario, however, in which only a fast lens will suffice, and that’s when you want a really tight depth of field, so that you can isolate the main subject in a scene by blurring out the background or foreground, or both. A 70-200mm f/2.8 zoom will give a tight depth of field, especially at the long end of its zoom range, but an f/1.4 lens takes minimising depth of field to a new level. Again, longer focal lengths of 50mm to 85mm help to shrink the depth of field still further, but even a 35mm f/1.4 lens can work well for this, especially if you get close to the main subject and use a short focus distance. Let’s see what competing f/1.4 lenses have to offer…