The Tech Zone shows what to look for when buying a digital camera lens.

You've seen the claims: "This is the sharpest lens I have ever used." But how does a person know whether or not a lens is truly sharp? And is sharpness the only criteria by which we should decide to use a lens? As someone with more than three decades of photo experience, I have used nearly 100 different lenses in my career. Some I liked more than others. And in an attempt to help photographers make informed choices, here is a primer on how to evaluate a lens.

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