Canon® EOS Digital Photography Photo Workshop

4.5. WHAT MAKES A LENS GOOD?

What makes a good lens can be argued on a scientific basis or according to aesthetic considerations. Most people want a lens that produces a tack-sharp image with great color rendition for superior image quality. Certainly, how the lens handles mechanically is also important; it has to function as the photographer's instrument and be able to be "played" without disrupting the creative process with limited functionality.

Canon outlines six primary characteristics of an ideal lens:

• Complete photographic quality. Truly great lenses feature both superior resolution as well as contrast across their entire surfaces. By using a more-than-sufficient amount of high-quality glass and optical coatings backed by sophisticated technology and engineering, resolution and contrast (which often work against each other) are optimized.

• Consistent color reproduction among all lenses. A primary goal of Canon optical engineering is consistency and uniformity of color reproduction no matter which interchangeable lens is being used.

• Out-of-focus quality. For photographers, what's out of focus is often as important as what's in focus. This natural "blur" effect using narrow depth-of-field is critical to representing a three-dimensional subject in a two-dimensional image, so it has to look believable and natural "which is yet another factor that's part of lens design and engineering.

• Ergonomic functionality. A lens needs to be comfortable, functional, and easy to use. While an ...