As the diagram below shows, the image produced is either stretched or compressed in a non-linear way making accurate measurements very difficult. Although there are software methods available to correct this, they cannot take the physical depth of the object into account and it is always preferable to choose a good quality lens rather than attempt to correct these errors in software.
As a general rule, a shorter focal length lens will have significantly more distortion than one with a longer focal length, as the light hits the sensor from a greater angle. Some lens manufacturers have put time and effort into overcoming this problem by using the best designs and materials available.
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