How the lenses are selected?
The lens selection is based on the working distance, component size, focal length and variations in any of the three. But there are specific thumb rules for the type of lens selection. It is better to use mega pixel lens for the mega pixel camera. Whenever the imaging requires perfection at the edges, better to go for tele-centric lenses or as a thumb rule the measurements using dimension requires tele-centric lenses.
