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

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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…






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