Beyond the Kit Lens
O.K. You got your new compact DSLR with the standard kit lens. Now assuming your DSLR contains a APS-format sensor with a 1.5 or 1.6x factor, your kit lens is probably a zoom of about 18-or-so to 50-something millimeters. The lens covers your wide-angle needs for landscapes and cramp-quartered group shots, and long enough to snag a tight headshot of junior cuddling (strangling?) the family cat.
For many folks the kit lens covers all bases, and as long as there aren't any African safaris on the horizon, they'll probably be happy for years to come. But you're different because you've been seduced by the joy of taking pictures, and you're ready for your next lens… or two. I know all too well because at one point in time I had 11 lenses in my personal arsenal. And yes, I used them all!
The first thing to ask yourself is do I want to go wider or longer? In other words, are you frustrated because your kit lens can't get you in close enough, or do you find yourself with your back against the wall because you can't back up far enough?
For many people the choice of a second lens is based on the need to go longer (telephoto) or shorter (wide angle). For longer focal length needs, there are many options available in zoom and fixed configurations. For wider needs, assuming your kit lens already has a field-of-view equivalent to 28mm lens, the options are fewer.
If you already own one of the above-mentioned kit lenses and you want to go longer, there are many options available in the 70-200mm range, which on the typical compact DSLR is an equivalent to about a 105 to 300mm lens on a 35mm camera. This is quite a nice range, and is also about as long as you want to go if you plan on working without a tripod, especially if you plan on purchasing a lens without image stabilization.
A Tale of Four Lenses
If you take a look at Canon's current line-up of tele zooms you'll notice you have a choice of four 70-200mm L-series lenses. Two of these lenses open up to a maximum aperture of f/2.8, two open up to a maximum of f/4, and one of each is an image stabilized (IS) lens. The non-IS f/4 lens sells for under $600, and the IS version costs a little over $1,000.00. The non-IS f/2.8 lens sells for around $1140, and the IS version costs about $1,700.00. Now here's the kicker- each of these zoom lenses is terrific and from a sharpness point-of-view are nearly identical, yet there's a thousand dollar point spread between them. Confused? Read on.
There's a one-stop difference in speed between f/4 and f/2.8. On the surface one stop seems to be a minor difference, but keep in mind the f/4 versions of these lenses are about one-third smaller, one-third lighter, and hundreds of dollars less expensive than their faster brethren. And they're just as sharp. Now under low lighting conditions, will the f/2.8 image stabilized version deliver a better/sharper image than the slower non-IS lens? Most probably yes. But if you work with a tripod, monopod, or other stabilizing device you can in most cases nail an image that rivals the ‘best' of the bunch.
About the only thing the f/4 lens will not be able to do is deliver the narrower depth of field afforded by the f/2.8 lens, and that's the next part of the equation. Faster lenses, be they fixed or zoom, allow you to isolate your subject from the background.
Your 28-80-something millimeter kit lens, set to the 50mm position has an effective aperture of about f/4.5, which delivers an image will most likely contain identifiable – and often distracting –detail in the foreground and/or background.
The same picture taken with a 50mm lens with a maximum aperture of f/1.4, f/1.8, or even f/2 has a far different look. Used wide open, there are only blurry tones where details appear in the kit lens image. And if you want more details in the foreground and background with the faster lens, all you have to do is stop the lens down.
If you want a wider-angle lens and you're shooting with a compact DSLR the choices are narrower and from an f-stop point-of-view, noticeably slower. Regardless of brand, the widest, non-fisheye fixed focal length lens you're going to find is a 14/2.8, which on a full-frame DSLR is really wide. On a compact DSLR these ultra-wides are the equivalent of a 21mm or 22.4mm lens, depending on your camera. As for price, they range from $579 to $1999.
A selection of 14/2.8 ultra-wide lenses from Canon, Nikon, Pentax, Sigma, & Tokina
Your other option for shooting wide with compact DSLRs are ultra-wide zooms, which are available from most all manufacturers. Optimized for use with APS-format sensors, compact ultra-wide tend to be noticeably slower in the f/stop department. The good news is ultra-wides, because of their greater angle-of-view, are easier to successfully hand-hold under low light conditions.
Just as Canon offers four variations of their 70-200 L-series lenses, they offer a somewhat similar choice at the wide end of the optical range, specifically Canon's 16-35/2.8L EF and 17-40/4L EF. Both are L-series lenses (Canon's best), but here's the kicker on this duo- the slower, less expensive 17-40/4L is equal to, and perhaps a tad sharper at the edges than its slightly wider, one-stop faster brother. Now if you need the extra millimeter and/or the additional stop of light, the 16-35/2.8 makes sense, but for $700 less you can buy a first-class wide zoom of equal quality.
Focal length aside, what other needs do you have? Is your variable aperture kit lens sufficient or do you need a faster, wide aperture for low-light shooting? Or perhaps you can get away with an image-stabilized (IS), variable aperture lens? If your camera is already equipped with a built-in IS system, you're half-way home.
Image stabilized cameras and lenses are quite good at what they do. Thanks to IS technology it's possible to capture sharp images at shutter speeds 3 to 4 times slower than normally possible. But while IS technology makes it possible to hand-hold an f/5.6 lens at shutter speeds normally reserved for an f1.4 lens, the look of an image at f1.4 is far different than the same image captured at f/3.5, f/4, or f/5.6.
See ‘Fast Glass'
There's no denying the fact variable-aperture lenses are far lighter - and hence more likely to spend the day with you – than faster optics, but there are other factors to consider. If your zoom lens tops out at f/5.6 at the telephoto end of the zoom range, and you plan on shooting through a Polarizing filter or use a 2x tele converter, your widest aperture will now effectively drop 2-stops to f/11, which is darned slow. To add insult to injury most autofocus systems start pooping out at about f/8, which means if you're not shooting under high-noon sunlight, you're skunked. And in case you're wondering, a Polarizer and a 2x teleconverter turn f/5.6 into an all but useless f/22… and that's wide open.
Lens construction is another reason why some 70-300mm zooms cost $109.99 and other 75-300mm zooms cost 10x that amount. Plastics have their place in the world and polymers have enabled manufacturers to produce cost-effective, yet decent lenses for our cameras. But if you plan on using your gear frequently, and in less than ideal environments (the beach, on the water, on the slopes, hiking glaciers, or the tropical boulevards of Boca Raton) you might want to purchase a lens that can withstand the rigors of life beyond the padded case. Metal alloy construction and silicon gaskets add to the physical integrity of the lens, which also means you're more likely to be enjoying your lens ten-or-more years from now.
Needless to say the costlier lens probably contains a higher grade of glass, i.e. extra-low dispersion glass with aspheric glass surfaces, which enable higher resolution, better detail at larger print sizes, and better overall color fidelity. Costlier zoom lenses are also less prone to drift when working on a tripod and aiming the lens up or down, and if you've owned a ‘drifter' you know how annoying this can be.
Another need you might have is the ability to shoot extreme close-up imagery. While many lenses tout close-up, or macro abilities, they are not true macro lenses. Macro lenses are flat-field lenses, which means if you focus straight onto a flat surface containing text, the text appears sharp edge to edge even at wide aperture. A conventional lens with close focusing abilities might be sharp in the center of the image area, but a box of donuts says the edges will be soft at wide aperture. Depending on the lens you're using and how tight you get to your subject, the edges might still be soft even after you stop down to smaller apertures.
For 35mm cameras, macro lenses are available in 3 focal length ranges; normal (50-70mm), short telephoto (90-105mm), and longer telephoto (150-200mm). All of the macro lenses shown above focus down to life-size (1:1) with the exception of Canon's 50/2.5 macro, which goes down to half life-size (1:2). As for why you'd want a telephoto macro lens, just try photographing a dragonfly from 6-inches away. Longer focal length macro lenses are also useful in the studio where the camera and lens can easily get in the way of lights and umbrellas.
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