Ross Xpres
Revision as of 23:22, 25 February 2011 by Dustin McAmera (talk | contribs) (Repaired photo link. Rewrote text a little; unfair to imply the Xpres was designed simply to get round the Tessar patent)
The Xpres is a very successful lens made by the British maker Ross. It may be described as a modified triplet, similar to the Tessar[1], except that whereas in the Tessar the rear group is a cemented pair of elements, the rear group of the Xpres is three glass elements cemented together. This was potentially an improvement on the Tessar design[2].
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| Xpres 5½ inch f/4.5 on a Thornton-Pickard plate camera. image by Ebay seller Watchoutbeetleabout (Image rights) |
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| Xpres 105 mm f/3.8 on an Ensign Selfix 820 image by Tim Pickford-Jones (Image rights) |
Notes
- ↑ That is to say, it is easiest to describe a Tessar by describing how it differs from a simple triplet, rather than implying any particular design process; Kingslake, Rudolph, A History of the Photographic Lens (1989). "It is certain that the Tessar was not a modified Cooke Triplet, as the series of steps followed by Dr. Paul Rudolph in going from the Anastigmat to the Tessar are well established, but for some of the later designs it is not always clear whether they should be regarded as modified Tessars or modified Triplets."
- ↑ Greenleaf, Allen R., Photographic Optics (1950), Macmillan, New York. "The Ross Xpres is a further development of the Tessar construction; the rear component is made up of three glasses instead of two, providing still more possibilities for correction of aberrations."
