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| | Articles - Aberration in optical systems (via CobWeb/3.1 planetlab2.georgetown.edu) (Site not responding. Last check: 2007-10-13) |
 | | These constants are determined by the data of the system (radii, thicknesses, distances, indices, &c., of the lenses); therefore their dependence on the refractive index, and consequently on the colour, are calculable (the formulae are given in Czapski-Eppenstein, ´´Grundzuge der Theorie der optischen Instrumente´´ (1903, p. |
 | | If a constant of reproduction, for instance the focal length, be made equal for two colours, then it is not the same for other colours, if two different glasses are employed. |
 | | On this account the lines D and G´ are united for ordinary photographic objectives; the optical as well as the actinic image is chromatically inferior, but both lie in the same place; and consequently the best correction lies in F (this is known as the ´´actinic correction´´ or ´´freedom from chemical focus´´). |
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