Darlot Hemispherique Lenses

[william linne]

Can someone give me some info on these lenses and the differences between the various numbers (Hemispherique #1, #2,etc)?

thanks,

Wiliam

[Ernest Purdum]

I aaume you are referring to the "Hemispherique Rapide", since I have noit seen the designation "Hemispherique" used by itself. These are an early form of wide angle lens. The Darlot company traces right back to before the time the time of Daguerre. It was founded by Jean T. Jamin in 1822, then Alphonse Darlot took over in 1860.



The lens is probably a form of Rapid Rectilinear with the groups close together and the elements given strong curves. It is unusual in having pivoted stops worked by little levers extending out of the barrel. As a relatively slow wifde angle, four total stops were adequate, so the pivoted stops, which can't be lost, were a better choice for this lens than the Waterhouse stops needed by lenses which required a wider choice of aperture.



The numbers, #1, #2, and so on, refer to the focal length. Number 1 is not necessarily the smallest, since some makers had a size 0 and sometimes 00, and 000. Dagors came in sizes down to 0000.