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the Canon FL-F 300mm f/5.6 telephoto lens. Fluorite has some drawbacks, for example vulnerability to sudden changes in temperature, and thus attempts were made to use substitutes, such as fluorophosphate glasses, which ameliorate, but do not completely eliminate (as compared with ordinary glass) these drawbacks.
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Often, however, apochromatic lenses used in fine cameras are not termed apochromats, Instead, they may be simply called "fluorite lenses", based on the material with anomalous partial dispersion which allowed them to be apochromatic. Such lenses began to be available to photographers in 1969, with
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and dispersion must be accounted for during apochromat design to assure good optical performance over reasonable temperature ranges with only slight re-focusing. In some cases, apochromatic designs without anomalous dispersion glasses are possible.
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Also, when considering lens design, the "APO" designation is used more conservatively in astronomy-related optics (e.g. telescopes) and microscopy than in photography. For example, telescopes that are marked "APO" are specialized,
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is the phenomenon of different colors focusing at different distances from a lens. In photography, chromatic aberration produces soft overall images, and color fringing at high-contrast edges, like an edge between black and white.
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process (copy) cameras generally use apochromatic lenses for sharpest possible imagery as well. Classically designed apochromatic process camera lenses generally have a maximum aperture limited to about
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7. Focused and guided properly during the exposure, these apochromatic objectives are capable of producing the sharpest wide-field astrophotographs optically possible for the given aperture sizes.
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Telescope objective lenses for wide-band digital imaging in astronomy must have apochromatic correction, as the optical sensitivity of typical CCD imaging arrays can extend from the
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Apochromatic lens brings three colors to a common focal plane. Notice that this lens is designed for astronomy, not viewing, since one of the wavelengths (~0.780
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wavelength range. Apochromatic lenses for astrophotography in the 60–150 mm aperture range have been developed and marketed by several firms, with
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Independent tests can be used to demonstrate that the "APO" designation is used rather loosely by some photographic lens manufacturers to describe the
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of their lenses, as comparable lenses have shown superior color accuracy even though they did not carry the "APO" designation.
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that are optimised for infinity-like distances whereas in photography, even certain relatively low-priced general-purpose
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9. More recently, higher-speed apochromatic lenses have been produced for medium format, digital and 35 mm cameras.
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The
Apochromatic lens usually comprises three elements that bring light of three distinct colors to a common focus
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Chromatic aberration of a single lens causes different wavelengths of light to have differing focal lengths.
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463:"A 300mm f/2.8 photographic lens without the "APO" designation, tested for chromatic aberration"
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438:"A 300mm f/2.8 photographic lens with the "APO" designation, tested for chromatic aberration"
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properties to achieve three color crossings. This is usually achieved using costly fluoro-
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Focus error for four types of lens, over the visible and near infrared spectrum.
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colors into focus in the same plane – typically red (~0.620
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Apochromatic designs require optical glasses with special
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at two wavelengths, rather than one as in an achromat.
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219:in the same plane – typically red (~0.590
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196:face similar problems, particularly with
117:Learn how and when to remove this message
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231:chromatic lenses are designed to bring
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420:"What do APO and Apochromatic mean?"
55:adding citations to reliable sources
180:, meaning free from or away from.
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176:comes from the Greek preposition
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368:are given the APO designation.
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208:lenses are corrected to bring
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200:that use lenses rather than
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165:than the much more common
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524:Microscope components
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348:Use in photography
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426:. Lenses FAQ.
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66:"Apochromat"
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49:Please help
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18:Apochromatic
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335:, abnormal
272:ultraviolet
213:wavelengths
194:Astronomers
184:Explanation
172:The prefix
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498:2011-03-25
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448:2011-03-28
424:stason.org
406:References
329:dispersive
206:Achromatic
198:telescopes
139:apochromat
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159:chromatic
153:or other
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