And how to reduce it, and get the sharpest images possible.
White light is made up of a complete spectrum of different wavelengths of light. The visible wavelengths range from 400 nano-metres (violet) to 700nm (red). When a simple lens focuses light, the different wavelengths are focused at slightly different distances. In a photograph, this would result in coloured fringes around edges of subjects. Camera lenses generally have multiple elements for exactly this reason. Most lenses are chromatically corrected, so all visible light is all focused at the same point. Of course, there are good and bad lenses; following the following guidelines will generally result in less chromatic aberration:
- Where possible, avoid zoom lenses. fixed focal length lenses reduce chromatic aberrations more effectively.
- Avoid zoom lenses with too much range. These ‘superzooms’ handle aberrations pretty badly.
- Stop down the aperture (use a large f-number). Try never to use the maximum aperture.
- Buy quality
In addition to visible light, digital sensors (and film) are also sensitive to ultraviolet and infrared wavelengths. As lenses are generally only corrected for visible light, to get the sharpest images you should ensure no UV or infrared light gets through the lens. This can be filtered (using a UV filter is good standard practice) or if you are using artificial light, a better solution is to use lights that don’t have any non-visible element. White LED lights have only light between 400 and 700nm, and recent LED lights are now bright enough for high speed imaging (the Constallation120 has the light output of a 1.5kW tungsten spot). There are also other benefits, including zero heat. See more information on LED light technology here.