How to Buy Lenses for Your Digital SLR

If you're one of the millions of people who have bought your first Digital SLR camera, you're probably in a quandary as to what kind of lenses to buy. Here's a quick guide to DSLR lenses.

Steps :

1. Understand the terminology before you buy: "Wide-angle" is generally considered any focal length below 35mm, and shows a wide field of view. "Standard" or "mid-range" focal lengths can range from 35mm to around 80mm, and are closer to what the human eye sees. The "telephoto" range is generally considered to be any focal length from around 85mm and higher, and is used to make subjects appear closer. A "prime" lens has only one focal length, such as a 50mm lens. A "zoom" lens covers multiple focal lengths, and is described (for example) as an 18-55mm lens, meaning it covers a range from wide-angle (at 18mm) to mid-range (at 55mm).

2. Define your need: After using your camera with whatever lenses you have now, you may find that you can't get the photos you want because your subject is often too far away, or your subject may often be too large to get all of it in the picture. Or, perhaps your current lens's image quality is poor. That will help you figure out which lens to purchase.

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3. Mid-range zoom: This is a lens with a focal length of approximately 18-70mm. You'll probably use it for 75% of your shooting. Luckily, all DSLR makers offer a "kit" lens in this range, and most discount it heavily if you buy it with the camera. The optical quality is generally very good for the price. It's pretty much a no-brainer -- grab it.

4. Telephoto zoom: This is probably the lens you'll buy next. Commonly used for nature photography, sports, or any time you want to take a "close up" of a distant object.

5. Wide angle zoom: Get out your wallet -- there are no bargains here. WA zooms are fiendishly tricky to make and you'll pay top dollar. A 10-20mm will cost about as much as you paid for the camera, but the results are worth it (assuming you like the exaggerated geometric effects, which tend to make people look just weird). Since not many folks will shell out for a WA zoom, your super-wide pix will really stand out.

6. "Normal" lens: A lens that covers a modest angle of view is simple to design to perform well at wide apertures with cheap materials. A 35 to 50mm f/1.7 - f/2 lens is great for low light and portraits. For whatever reason the 50mm is generally much cheaper; it will give a somewhat narrower angle of view on consumer (small sensor) DSLRs and work on film and full-frame digital too. It will have excellent image quality.

7. Quality: Virtually all prime lenses are better than a zoom lens that covers the same focal length. Similarly, a lens that zooms from wide-angle to telephoto sacrifices image quality to provide convenience.

8. One-lens system: A mid-range zoom such as an 18-55mm or 24-70mm will cover most photos you'll want to take. Lightweight and easy to use, most photographers primarily use a lens in this range, referred to as their "walkabout" lens.

9. Two-lens system: If you only want to carry two lenses, use a wide-angle zoom like an 18-55mm, and pair it with a good telephoto, such as a 75-300mm. You'll find a number of lenses in each of these ranges, with image quality and prices that vary widely. This will give you coverage from wide-angle through telephoto.

10. Finished.

Source : http://www.wikihow.com/Buy-Lenses-for-Your-Digital-SLR