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Camera Lenses
Posted On 09/24/2010 11:48:57 by administrator

Understanding camera lenses can help add more creative control to digital photography. Choosing the right lens for the task can become a complex trade-off between cost, size, weight, lens speed and image quality. This tutorial aims to improve understanding by providing an introductory overview of concepts relating to image quality, focal length, perspective, prime vs. zoom lenses and aperture or f-number.

All but the simplest cameras contain lenses which are actually comprised of several "lens elements." Each of these elements aims to direct the path of light rays such that they recreate the image as accurately as possible on the digital sensor. The goal is to minimize aberrations, while still utilizing the fewest and least expensive elements.

lens elements diagram

Optical aberrations occur when points of the image do not translate back onto single points after passing through the lens, causing image blurring, reduced contrast or misalignment of colors (chromatic aberration). Lenses may also suffer from uneven, radially decreasing image brightness (vignetting) or distortion. Try moving your mouse over each of the options below to see how these can impact image quality for extreme cases.

Original ImageLoss of ContrastBlurringChromatic AberrationDistortionVignettingOriginal

Any of the above problems is present to some degree with any lens.  In the rest of this tutorial, when a lens is referred to as having lower optical quality than another lens, this is manifested as some combination of the above artifacts.  Some of these lens artifacts may not be as objectionable as others, depending on the subject matter.

Note: For a much more quantitative and technical discussion of the above topic, please see the
tutorial on camera lens quality: MTF, resolution & contrast.

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