How to Buy a Camera Lens
Are you looking to buy a new lens for your digital SLR camera? With so many to choose from, it can be hard to find the most suitable one. Generally, when it comes to purchasing lenses, you get what you pay for; but for high-quality photography, you need to look at more than the price tag. So, when the time comes to purchase your next lens, consider the following five criteria.
It's important to know what type of photography you plan to use your new lens for, because some focal lengths are especially suited to specific shooting situations. For instance, wide-angle lenses that cover a range of between 10mm and 20mm are most appropriate for landscape or architectural shots.
Long zooms (measuring 300mm or more) are best for wildlife shooters. Portrait lenses typically come in at between 50mm and 100mm, but 70mm-to-200mm zooms may fall into this category as well. If you're just looking for an all-purpose lens, aim for something that spans a range of focal lengths, such as 18mm to 200mm.
Fixed Aperture vs. Variable Aperture
Camera lenses have either a fixed aperture or a variable aperture. Fixed apertures permit the maximum amount of light to enter your camera at any focal length, which in turn gives you the greatest amount of versatility; unfortunately, such lenses will almost always be accompanied by higher price tags.
Variable-aperture lenses cover a range of maximum apertures like f3.5 to f.5.6. Though some very good lenses have variable apertures, they usually don’t have the same optical quality as a fixed-aperture equivalent, and they aren't as useful for shooting great photos in low-light situations.
Zooms vs. Primes
Zoom lenses are meant to work across a range of focal lengths. This makes them very adaptable lenses, ensuring that you won't have to change lenses as often to get the shot you want. On the other hand, you have to make certain compromises to achieve that flexibility. Barrel distortion or pincushioning may be present at the extreme focal lengths of your zoom, and image sharpness may suffer.
Prime lenses have a fixed focal length. Because they were manufactured with that focal length in mind, they suffer far less from the drawbacks listed above. They'll almost always be optically superior to zooms, and in most cases they'll be more durable, too. However, prime lenses cost significantly more than zoom lenses.
Stabilized vs. Nonstabilized Lenses
Image stabilization is a great advantage for photographers because it helps counteract the effects of camera shake, so you can shoot successfully at shutter speeds that you wouldn't normally get away with.
Camera manufacturers agree that image stabilization is good, but they are split on how best to incorporate it. Nikon and Canon build it into almost all of their new lenses, but Sony and Pentax prefer to build a sensor shift system into the camera body. Both do much the same job, but in-camera stabilization may entail lower lens costs, and it enables users to attach any modern lens to their camera and still get the benefits of image stabilization.
HD Video Lenses
Very few lenses are specifically designed for recording HD footage on a digital SLR camera. Nevertheless, some lenses produce better HD video results than others. Ideally you'd buy large aperture prime lenses equipped with easy-to-adjust manual focus rings. Once again, prime lenses usually provide you superior optical quality, and a large aperture is the best choice for shooting in low-light situations and controlling depth of field.
Autofocus is almost indispensable these days for still-image photography, but it remains an evolving technology for video. Many DSLRs are slow to focus accurately; others record the faint whine of an autofocus motor in the background. So, if you're serious about shooting HD video, you should probably look to manual focus to achieve the effects you want.