"Focal length" Quotes from Famous Books
 ... of Cambridgeport, Boston, Mass. One of their most famous telescopes is the great Lick Refractor now in use on Mount Hamilton in California. The diameter of this object-glass is thirty-six inches, and its focal length is fifty-six feet two inches. A still greater effort has recently been made by the same firm in the refractor of forty inches aperture for the Yerkes Observatory of the University of Chicago. The telescope, which is seventy-five feet in length, ...
— The Story of the Heavens • Robert Stawell Ball
... was merely a large collector of moonlight, which was thrown after collection onto a lunium plate. The resultant emanations were turned into a parallel beam by a parabolic reflector and focused, through a rock crystal lens with an extremely long focal length, onto ...
— Astounding Stories of Super-Science April 1930 • Various
... of reproduction is equal for two different colours, i.e. this constant is achromatized. For example, it is possible, with one thick lens in air, to achromatize the position of a focal plane of the magnitude of the focal length. If all three constants of reproduction be achromatized, then the Gaussian image for all distances of objects is the same for the two colours, and the system is said to be in "stable ...
— Project Gutenberg Encyclopedia
... simple construction. The essentials of a good stand camera are that it shall be rigid, possess a rising and falling front, a swing back, and bellows which will be capable of extension to fully double the focal length of the lens to be used ...
— How to Observe in Archaeology • Various
... carriage that holds the lens, and is connected by bellows-work with A. In my apparatus it is pushed out and in, and clamped where desired, but it ought to be moved altogether by pinion and rack-work.[24] The lens I use is a I B Dallmeyer. Its focal length is appropriate to the size of the instrument, and I find great convenience in a lens of wide aperture when making the adjustments, as I then require plenty of light; but, as to the photography, the smaller the aperture the better. The hole in my stop is only two-tenths ...
— Inquiries into Human Faculty and Its Development • Francis Galton |
