Discoveries and inventions of the nineteenth century (1905)
Routledge, Robert · London : G. Routledge and Sons · leaf 669
on focus. Such are the lenses always used in thephotographic camera, and the skill of the optician is taxed to so combinethem as to obtain, not only the union of the principal rays in one focus,but the greatest possible flatness of field in the image, the largest amountof light, the widest angle… … Fig. 310. astronomical telescopes. Mr. Dallmeyer has made photographic lenseswhich cost upwards of ^250; but it is doubtful whether the pictures formedby these would show any marked superiority over those produced by lensescosting only one-fifth of that amount. Fig. 310 shows the construction ofthe…
Inventions
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