Many budding photographers forget that convenience and flexibility frequently come with a cost, and zoom lenses are far from being an exception.

Here are some disadvantages of zooms that you may not be aware of:

  • Zoom lenses are slow - No, I don't mean the amount of time it takes to zoom in or out. We're talking the amount of light that's allowed in. Whereas a 50mm non-zoom (prime) lens may open all the way up to f/1.8 or more, typical mid-priced zoom lenses in that focal-length range aren't any faster than f/4 to f/5.6, and many get worse as you zoom in further.
  • The image quality isn't as good - A cheap prime lens will almost always beat out a mid-priced zoom lens when it comes to sharpness and image detail. The reason for this is that zoom lenses typically have up to twice as many elements (individual pieces of glass that comprise a lens) as a non-zoom lens within the same focal length range, and it's harder to engineer a lens with this much glass to produce a very good picture.
  • Zoom lenses are heavier - More glass in the lens and more mechanics to move it means a heavier lens.

Of course, these disadvantages can be greatly outweighed by the flexibility that being able to zoom offers. However, if you own an SLR, either film or digital, it is usually good to own at least one or two prime lenses, such as a 50mm f/1.8 or better and a 28mm for those wide-angle shots. You'll thank yourself when you end up in a low-light situation and don't want to or can't use flash; museums don't really care how slow your film is and won't bend their policies to accomodate you.