Auteur: Dan Fromm
Date: 07-09-2006 16:09
Selon le Vade Mecum, "Gasc et Charconnet, Paris.
They introduced Harrison's Globe lens to France as "Lentiforme de l'oeil" and they supplied details to M.van Monckhoven for his book (p125). Many of their other productions were Petzval lenses. Lenses have been noted with both Laverne and Gasc et Charconnet engraved on them. The glasses in the Globe were crown ?1.53 and flint ?1.60, and Monckhoven notes that as the light is always nearly normal to the air-glass surfaces there is a high correction of both distortion and astigmatism- it may in fact be the first true anastigmat. But it suffers from spherical aberration severely and for sharp work needs to
be stopped to at least f36 and possibly f72- below this it sufferes from diffraction. It covers at least 75° and a 10cm lens covered 14x12cm format. It was freer from distortion than the Ross (Actinic) Doublet and increased speed at a given aperture- and compared with the Periscopic it was colour corrected. It also tends to give dark foregrounds in prints- (probably due to flare) and lacks brilliancy."
JCL, c'est le press-papier de vos reves!
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