"Focal length" Quotes from Famous Books
 ... 5 or 6 in. in length; after working 5 hours hold the speculum in the sunshine and throw the rays of the sun onto a paper; where the rays come to a point gives the focal length. If the glass is not ground enough to bring the rays to a point within 5 ft., the coarse grinding must be continued, unless a longer focal length ...
— The Boy Mechanic: Volume 1 - 700 Things For Boys To Do • Popular Mechanics
... 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
... 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
... 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
... 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 |
