**1. What kind do I need? **
The best way to answer this question is to make a short list of what annoys you when shooting. If slow shutter speeds rankle, you’ll need a larger maximum aperture or image stabilization. If you can’t fit everything in the frame, you’ll want to go for a wider focal length. But if you need to get closer, you’ll need a longer telephoto.
Or consider what you like shooting best. Enjoy birding? Go for a long stabilized zoom or prime. Do you like architectural or street photography? Then a tilt-shift or wide-angle prime with low distortion should appeal to you. Frustrated by slow shutter speeds when your kit zoom is racked out? Try a faster step-up zoom.
**2. Prime or zoom? **
A prime lens often shows less distortion than a zoom lens would at an equivalent focal length. Similarly, a zoom’s sharpness varies across its focal range, so depending on the focal length you use most, you might get greater image quality for your buck from a telephoto prime than a long zoom. Check your EXIF data—if you notice yourself shooting primarily at a given focal length, a prime lens at that length might be the one for you. Shoot across a range of focal lengths? Remember that a zoom lens isn’t a compositional tool. Make sure that when you shoot, you choose a focal length for its characteristics of compression and the ways its field of view helps you tell a story. If that’s how you use it, a zoom upgrade may be right for you.
3. Variable aperture or constant?
A constant maximum aperture can be extremely helpful when shooting at a zoom lens’s longest focal length. However, that benefit typically comes with a hefty price tag. A constant f/4 will be more affordable than a constant f/2.8, though, and we’ve seen many more of these recently since Canon and Nikon put out their more affordable full-frame bodies. If you’re not satisfied with your kit zoom’s f/3.5–5.6 range but don’t have a fortune to spend, look for an f/2.8–4 from a third-party lens maker or a constant f/4.
4. Tired of relying on your kit lens?
When using an APS-C-size sensor, an 18mm gives you a full-frame field of view similar to a 28mm. The 55mm becomes equivalent to about an 85mm. The most common second lens these days is either a 55–200mm to add reach, or a fast 50mm that can be great for portraits on APS-C DSLRs. However, an ultrawide zoom or a specialty lens (macro or Lensbaby, perhaps?) can be a nice way to jumpstart your creativity.
**5. Should I buy a third-party lens? **
A third-party lens is one made by a manufacturer other than the one that made your camera body. You’ll probably always be able to find some cheapo lens makers that you’re best to avoid, but third-party brands such as Sigma, Tamron, Tokina, and Zeiss make some wonderful glass and warrant consideration. Sigma’s 50mm f/1.4 is one of the sharpest normal lenses we’ve seen, and its 18–35mm f/1.8 is the fastest of its kind. Meanwhile, Tamron has the only optically stabilized 24–70mm f/2.8 full-frame lens that’s available today; the company consistently delivers all-in-one zooms that provide terrific bang for your buck. Tokina’s catalog is smaller, but its 12–28mm f/4 is a great way to go wide with an APS-C body.
6. Do I need optical image stabilization?
Technically, no one needs image stabilization if there’s a tripod around. But it sure does help. We’ve seen up to four stops of real-world handholding advantage from optical image stabilization systems in lenses. This means that if you normally have to shoot at 1/400 sec to get a sharp shot, you might be able to get the shot at 1/25 sec instead. That’s an extreme example, but often even one stop of compensation could be enough to get you out of a jam. Plus, you can see the stabilization as you frame, which makes for a less jittery shooting experience.
7. Should I buy a vintage or used lens?
Vintage glass can be a great way to get a unique look for your photos, but you will typically sacrifice a small amount of sharpness when adapting a lens from one system to another. Used glass can have drawbacks, but if the lens you’re interested in has been well maintained and was recently serviced, you might get pleasing results. Keep in mind that the latest lenses have coatings that can better suppress flare and often can better control chromatic aberration and distortion.
8. Can I test out a lens first?
Some photo retailers will let you bring your camera body into the store and mount a lens for a quick and simple look. If you want to spend some quality time with a candidate, we suggest renting, especially if you’re considering a very expensive lens.
9. How large is physically too large?
While we can’t speak for your back, ask yourself a few important questions. Are you willing to carry a large, heavy lens with you to the places you go (or plan to go) to photograph? Are you prepared to also get a larger case or camera bag if needed? Do you have the proper level of support, such as a tripod or monopod? If you answered no to any of these questions, then you might want to opt for smaller glass.
10. Which extras do I really need?
A protective filter or simple UV filter can be the one thing that saves your lens if the front of it comes into contact with something hard or sharp. We consider it a must-have. After that, you’ll most definitely want a microfiber cleaning cloth and perhaps another cleaning option, such as a LensPen. A blower brush can really come in handy in dusty environs. Other than those, a good case or bag is the only real necessity. More nice-to-haves are extension tubes to add close focusing abilities without a dedicated macro lens and a circular polarizing filter, which can reduce or eliminate glare in some tricky situations. Neither is absolutely essential and both can be added later.