Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . Fig 199.—Mont Blanc, as seen from Geneva ; taken by the Vega CompaujjTo face page 317. J. with a lens having a focal length of ten inches. - ? ^m? % -? •& jfe ,, -; - •• -r;^ . fc^K 4*0 Jb i$L££ k_ - (A >ift *,:F /-? * ^BB HiH^ii- ,... jfty mi ;%i-r. • I :,& ftrttt&V . i^&4* i : 1 jth a telephotoscopic lens of focal length fifty-three inches on a whole plate. PHOTOGRAPHIC OUTFIT FOR BALLOON WORK. 317 the most that can be done. The grain of the plate b
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . Fig 199.—Mont Blanc, as seen from Geneva ; taken by the Vega CompaujjTo face page 317. J. with a lens having a focal length of ten inches. - ? ^m? % -? •& jfe ,, -; - •• -r;^ . fc^K 4*0 Jb i$L££ k_ - (A >ift *,:F /-? * ^BB HiH^ii- ,... jfty mi ;%i-r. • I :,& ftrttt&V . i^&4* i : 1 jth a telephotoscopic lens of focal length fifty-three inches on a whole plate. PHOTOGRAPHIC OUTFIT FOR BALLOON WORK. 317 the most that can be done. The grain of the plate becomesenlarged in the process, and obscures all the detail, if it iscarried beyond a certain limit; and it is impossible in thisway to conjure up any detail that does not exist in the original. There is another method by which a magnified image can beobtained. A lens is used which produces a small image, andthis is enlarged by allowing the rays to pass through a secondlens, and then to fall on the sensitive surface. This is called atelephotographic method, the whole being actually a sort ofphotographic telescope. The first lenses of this kind weremade by Dallmeyer of London, and independently b
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
