Short Report: Sigma Zoom Combo
Two low-priced lenses from Sigma are ideal for photographers on a budget
If you're looking for a low-priced, compact set of lenses that offer a great range for small-format digital SLRs, check out Sigma's new pair, the 18-50mm ƒ/3.5-5.6 DC and the 55-200mm ƒ/4-5.6 DC. These are ideal all-around focal lengths offering wide-angle and moderate telephoto ranges. Designed specifically for digital cameras (indicated by the DC), this combo typically offers an equivalent focal length range of 27-300mm on a small-format digital SLR for a 35mm camera. The image circle of these lenses won't cover a standard 35mm film frame.
Very small and lightweight, these lenses balance a compact, lightweight digital SLR well. The 18-50mm lens is 2.3x2.6 inches and weighs only 8.6 ounces; the 55-200mm is 2.7x3.3 inches and weighs just 10.9 ounces. I used them with a Canon EOS Digital Rebel and found they made a compact, easy-to-carry package so I had a lot of focal length always with me.
One thing you do give up with such small lenses is maximum ƒ-stop. They're variable ƒ-stop lenses, meaning the maximum ƒ-stop changes with the zoom. At the maximum zoom settings, the maximum ƒ-stop is ƒ/5.6 for either lens. However, since most digital SLRs offer superb results at higher ISO settings, this isn't necessarily a problem.