Comment on Nikon 35mm f/1.8G AF-S DX Lens for Nikon Digital SLR Cameras by Glenn Carpenter.
Unassuming humble little jewel of a lens,
Nikon has absolutely nailed it with this lens. A modest sum gets you exactly what you need in a lens, nothing you don’t, and it works beautifully. It is relatively feature-rich at its price: cheap lenses, even from Nikon, often lack important features – but not here. Unlike other recent DX bargains this lens has Nikon’s M/A focus setting, which allows automatic focus with instant manual over-ride. This is a simple and intuitive method of combining the ease and accuracy of AF with sometimes-necessary manual control, and Nikon has done users of this lens a great favor by including it, despite the low price. It also features, less importantly, a proper metal mount and a gasket to keep dust ingress from occurring through the camera/lens interface. A couple of items do remain absent: there is no focus distance scale, and as a consequence there is no depth-of-field scale, an unfortunate omission that is nevertheless justified at the price point. This is a bargain lens, a no-brainer for any photographer aspiring beyond the point-and-shoot level, and the lack of distance and depth scales are a reasonable trade-off.
What is clear to me in using this lens is that Nikon has put its money in exactly the right places to make this lens a star despite its price. There may be nitpicks here and there, but the optics, the coatings, the engineering, and perhaps most importantly the quality of the focusing system, are exactly what they need to be to allow this lens to make photographs that are the equal of those made by professional zooms costing in the thousands.
The important thing to keep in mind with this lens is that it is a relatively fast prime lens, and the most important quality of a fast prime is its ability to take photographs using a large aperture: without this ability there are any number of excellent consumer and professional zooms that are capable of doing the same job. Its essential distinguishing quality, then, is its ability to make images at apertures wider than f/2.8 or so, and at such large apertures there are two hurdles that a lens must overcome. The first is simply a matter of optics: most lenses, historically at least, have been made from an assemblage of spherically-ground lens elements. Spherical elements do a good job of approximating the perfect shape for a lens at smaller apertures and are used because they can be manufactured inexpensively – but at larger apertures, their spherical nature varies optically from perfection, leading to something called spherical aberration. This results in a lack of acuity, and sharpness, in the resulting image. The 35/1.8 uses an aspherical element (actually a hybrid aspherical for what it’s worth) to correct this imperfection. The result, in this well-engineered example, is a lens that performs nearly as well at a wide-open f/1.8 aperture as at an optimal f/5.6 or f/8 aperture.
The other important hurdle in performance for a modern fast lens is the quality of the focusing system. This is more complicated than simply the lens itself, as it relies on electronics in both the lens and the camera body. Nevertheless the more I use Nikon’s AF-S lenses – and have the opportunity to compare them with older and third-party technology – the more I am impressed by their performance. The difficulty is that at f/1.8, even with a “normal” (35mm for DX) lens, the depth of field is very narrow. The focusing system needs to be able to find focus within a very small margin of error, and just as importantly it needs to be able to alter focus in very small increments in response to minor changes in the position of the camera or subject. The requirement for accuracy is stringent enough that earlier generations of AF lenses, those which relied on motors in the camera body, tended to be somewhat clumsy in their ability to consistently maintain perfect focus. They would “hunt,” requiring several back-and-forth adjustments to find perfect focus, and they would often either fail to respond or lose focus altogether when small adjustments were needed. Nikon’s AF-S lenses comprise a significant technical advance in that they largely eliminate these problems. The AF-S motors, in combination with the in-camera focusing logic of Nikon’s contemporary bodies, are able to make the small adjustments necessary to find and maintain focus even within small depths of field. They rarely hunt, they are typically very accurate, and the 35/1.8 seems to be as good as the best of them. This is important, because it allows the 35/1.8 get excellent, perfectly focused pictures while other lenses are trying to figure themselves out or are shooting pictures an inch or fractions of an inch out of perfection, often enough to ruin the shot.
These are the most important things to keep in mind, for most photographers, when looking for a fast “normal” lens. Everything else should be considered as well, but when it comes to the ability to…
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