Some Thoughts on Lenses

© 2009 Simon Hucko

I've already said my piece about buying a camera (point n shoot or DSLR). Time to focus on lenses (pun intended, sorry).

One of the main reasons to buy a DSLR is the ability to change lenses. With a compact camera, you're stuck with one lens that has to do everything you want it to. While it may be convenient to have a 20x zoom with "macro" focusing built into your camera, the quality of said lens is often rather terrible (especially out at the super-zoom range). Think "Jack of all trades, master of none." Having interchangeable lenses allows you to tailor the performance of your lens to the task at hand, resulting in much better quality. Like everything else in photography, lens design involves a series of trade-offs. I'll touch on a few of the major classes of lenses and some of the trade-offs that are made when designing and buying a lens.

Kit Zoom - These are the lenses that get bundled with consumer level DSLR's, typically 18-55mm. I also consider the 55-200mm lenses in this category. These lenses typically have mediocre optical performance coupled with cheap build quality and slow variable max apertures. Everyone starts here, but if you're serious about photography you'll quickly outgrow these lenses.

Super-zoom - Similar to the huge zoom range point n shoots, these lenses offer a one-stop solution to all of your photography needs. A common range here is 18-200mm for crop sensor cameras, or 28-300mm for full frame. Some go even more extreme, I've seen 18-270mm or 18-300mm from some of the 3rd party lens makers. Advantages: a good "travel" or "walk around" lens, it'll cover all the focal lengths you could need without having to switch lenses. This makes packing for a trip or strolling around the neighborhood easy, and you'll never be caught with the wrong lens on your camera. Disadvantages: Optical quality is often lackluster at best. Expect major distortion at both ends of the zoom range, vignetting, soft images, and slow apertures. Probably not something you're going to want to make 20x30 prints from.

Fast Prime - I've talked about these ad nauseum. I love 'em. See my first post about it here. Advantages: Relatively inexpensive, small, and light. Super fast apertures compared to zooms. Very sharp and distortion free, especially when using full frame glass on a crop sensor. Disadvantages: Price per extra stop of aperture skyrockets, primes also get more expensive the farther you get away from 50mm, optics are often somewhat soft wide open, very shallow depth of field when working wide open.

Fast, Fixed Aperture Zoom - These are the workhorses of the professional world, they typically come in 3 flavors from each manufacturer: a wide zoom (14-24mm f/2.8), a standard zoom (24-70mm f/2.8), and a telephoto zoom (70-200mm f/2.8). There's also a crop sensor equivalent of the standard zoom, usually somewhere around 17-50mm f/2.8. Advantages: Nice fast fixed aperture allowing for better working shutter speeds and more control over depth of field. Generally built like a tank, definitely designed for professional use. Optically some of the best lenses on the market. Disadvantages: Price is the major drawback here, with these lenses typically coming in around $1500-$2000, maybe even more. 3rd party manufacturers offer these lenses at lower prices, but the build quality is nowhere near as good. Weight and size are also drawbacks, as these lenses tend to be much larger than others with similar focal lengths due to the fast fixed aperture.

Macro - This is a popular specialty lens, as they're not too pricey and open up a whole new world of photography. A true macro lens will give you 1:1 or better, meaning the image on the sensor when focused in all the way will be the same size as the object in real life. Advantages: These lenses focus super close, and are designed to be super sharp when doing it. The only way to go if you're into close-up photography. Disadvantages: They're all prime lenses, meaning this is truly a specialty lens. Depending on the focal length it can also function as a portrait lens, but often they're slow to focus because they have such a huge focus range to move through. Also, they tend to have smaller maximum apertures than other primes in the same range (f/2.8-f/3.5), so it's not going to function as a "fast prime" in your kit. Finally, if you get into macro you're going to wind up with a big bulky tripod and some focusing rails to do it properly, so be prepared for the extra gear and expense. Note: Beware of zooms that promise "macro" focusing, they typically only get you 1:3 magnification or less. Sure, it's nice to have a close focusing zoom, but don't expect a true macro experience.

Super-Telephoto - If you're into wildlife photography, you can never have a lens that's too long (we're talking 400-600mm here). These lenses come in both zooms and primes, with the primes typically being faster and better quality. Advantages: There's no substitute for optical reach. If you want to photograph tiny objects far away, these are the lenses for you. They're also some of the sharpest lenses on the market. Disadvantages: Size and price. These lenses are huge, heavy, expensive, and require beefy tripods with specialized heads on them to handle the weight. Not something you're going to grab and go for a walk with, and you may need to take out a second mortgage on your house just to afford one.

Ultra-Wide - One of the initial drawbacks to crop sensor cameras was that it was hard to find a truly wide angle lens for them. This gap has been filled in the last year or so, and so there are a lot of wide angle zooms in the 10-20mm range. These lenses produce a very specific look, and definitely have some "wow" factor when used correctly. Advantages: Get some crazy perspectives with the huge field of view. Cover sweeping landscapes without the need to stitch together a panorama. Wide angle lenses also have greater depth of field, so it's easy to get more in focus. Disadvantages: Some serious perspective distortion possible, especially when shooting people: it'll probably take some work to figure out how to properly use this lens. Barrel distortion is prevalent, meaning you'll get a pseudo-fisheye look sometimes. This can be corrected in software, but is good to be aware of.

Fisheye - Definitely a specialty lens. Projects a 180 degree view onto your sensor with wildly distorted lines. Images can be "de-fished" in post, making these lenses ideal for quick and dirty panoramas (you can cover a 360 degree field of view in three shots). Advantages: Uber depth of field and field of view meaning you can pack a lot into your shot. Distortion effects can be used artistically. Disadvantages: The fisheye look can get old, quickly. This isn't a lens you'll be shooting all of your work with (hopefully), so it's up to you if you want to spend the money on a lens that will only get used occasionally.
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In the end, lens choices come down to a trade-off between zoom range, optical quality, size/weight, build quality, and price. You can often find excellent optical quality from the third party manufacturers (Sigma, Tamron, Tokina) for 1/2-1/3 the price of the Nikon/Canon equivalent. The downside there is that they typically skimp on build quality and generally have worse quality control than the major manufacturers, meaning you're more likely to get a lemon. Always do your research before buying a lens so you know what you're getting. I recommend the following sites for more information:

photozone.de has some excellent lens reviews. Unfortunately, they're a bit sparse when it comes to 3rd party lenses.
dpreview.com has only recently gotten into the lens review game, but they also do an excellent job with the limited selection available.
lensrentals.com gives some good real-world information with each lens. If they have the lens available for rent, that typically means it meets some minimum quality standard. They seem to be pretty honest with their reviews, and will note any major drawbacks to a particular lens.
amazon.com is a good place to get a general idea of what the lens is and how people feel about it. You won't get super specific lens testing (sharpness, etc), but you can get a general feel for the quality of the lens.
flickr.com is great because there's a group for just about every lens ever made. There you can read people's questions and problems with a lens and see images shot with it.

Hope that helps. Some day soon I'll write up a "which lens should I buy?" article, as the answer is a lot longer than you might think and this will serve as a nice reference for it. What's your favorite lens?

~S

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