Buying a Digital Camera - Zoom Lens with DSLRs May Offer a Surprise

SUMMARY: New to DSLR cameras? When purchasing a lens, you may be surprised at the true zoom magnification.

If you are new to DSLR cameras, consider this information before purchasing a digital camera or lens.

With compact and prosumer digital cameras, when you purchase a camera that has an optical zoom (ignore the digital zoom) with 33mm to 100mm or 36mm to 216mm, for example, the zoom you expect is the zoom you get. 33mm is a good wide-angle zoom factor, though better zooms are available, and 216mm provides a decent telephoto range. However, if you purchase for a DSLR camera a zoom lens with 18-200mm magnification, for example, you may not be getting exactly what you expect.

Most digital SLR camera users have to contend with a DSLR magnification factor, sometimes called a "focal length multiplier" or "crop factor". Without going into a whole lot of specifics that can be researched elsewhere, what this basically means is that when you attach a 200mm lens to a DSLR camera, you actually get a field of view equivalent to a lens with a greater telephoto zoom on a 35mm camera.

If the digital camera has a 1.6 focal length multiplier, such as the Canon Digital Rebel T1i, a 200mm lens will act as a 320mm, offering a greater telephoto zoom. Likewise, a 300mm ultra zoom lens will actually provide 480mm of zoom!

However, for a wide-angle lens, the effect is not so beneficial. A wide-angle zoom lens that supports 18mm zoom will actually provide ~29mm (28.8mm) zoom, which while it does not seem like much, does somewhat limit photo taking opportunities. So how can you compensate for this if an ultra wide angle zoom is critical to your photography?

* Spend more money (a lot more money may be required) and purchase a DSLR with no crop factor or a low crop factor.

* Look for ultra wide-angle zoom lenses. Depending on your camera, ultra wide-angle zoom lenses in the 12mm range, and possibly in the 10mm range, may be available. However, expect to pay several hundreds of dollars or more for these pricey lenses, and remember that the actual zoom will not be 10mm or 12mm but 16mm or 19.2mm (depending on your camera's magnification factor).

(image of Canon EF-S 10-22mm f/3.5-4.5 lens from Canon)