Wednesday, March 6, 2013

Calculate Lens Distortion

Lens distortion can create special effects, but most often photographers want sharper photos.


Photographers sometimes use lens distortion, an effect that causes images to be "spherised" or "inflated," as a special effect. More often, however, photographers try to avoid or correct the distortion by measuring it (or downloading software that tests image quality) and then using photo-editing software to correct the problem.


Instructions


1. Hang white rectangular peg board at eye level.


2. Download and print test charts (see Resources) or purchase them at a photography shop.


3. Place charts at various locations on the grid--center, top right, left, etc.


4. Shoot photos of the charts using different lenses. Make a note of each lens used for the various shots.


5. Test charts should be printed on matte paper to avoid glare.


Measure the number of reference lines that are bent as a percentage of picture height. For a more accurate reading, download images into a software program that will measure distortion.

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