photolithographic (fotolithografik)

photolithography (foto-li-thog'ra-fi), n. [F. photolithographic = Sp. fotolitografía; as Gr. φῶς (φωτ-) + E. lithography.] The art of fixing on the surface of a lithographic stone by the agency of the action of light upon bichromated gelatin combined with albumen, and by other manipulations, an image suitable for reproduction in ink by impre ion in the manner of an ordinary lithograph; also extended to include proce es of similar character in which the transfer is not made to stone; specifically, the proce of reproducing in ink any design or picture executed on prepared stone by means of photography, either directly or by transfers from photographs. The proce is analogous to several photo-engraving proce es executed on metal. See photolitho graphic proce , under photolithographic. Also called litho photography. 4455 photo logic (fō-to-lojʻik), a. [= F. photo log i que = Sp.fotológico =Pg. photologico; as photo log - y +-ic.] Of or pertaining to photo logy. photo logical (fō-to-lojʻi-kal), a. [ The painter should never forget that his notion of colour (as compared with that of the phot ologist ) is a negative one. n. Herschel, Light, § 48. [F. photo logie = photo logy (fō-tol'ō-ji), Sp. fotología = Pg. photo logia, photophone tinted dark gla is used to cause the apparent extinction of a star viewed through it. The thickne of the wedge at the point where the star vanishes determines its brightne . Wheel photometer, an instrument in which the light to be measured is weakened in any required degree by transmi ion through adjustable apertures in a rapidly revolving wheel. photometric (fō-to-metʻrik), a. [= F. photo métrique = Pg.photo met rico; as photometr - y + -ic.] Pertaining to photometry, or the measurement of the intensity of light, or to the photometer, or instrument by which this is effected; employing or made by a photometer: as, pho to metric researches or observations. - Lambert's photometric law [named after Johann He in rich Lam bert (1728-77), an eminent mathematician and logician, the discoverer of this law), the fact that a smooth, irregularly reflecting surface appears equally bright under whatever angle it is seen. - Photometric standard, a carcel lamp burning 42 grams of refined colza-oil per hour, with a flame 40 millimeters high. It is equal to 9.5 British or 7.6 German standard candles. The unit of photometry adopted by the Electrical Congre at Paris (1884) is the amount of light emitted from a surface of one square centimeter of melted platinum at its temperature of solidification; in 1889 one twentieth of this unit was adopted as the practical unit, and called a candle. See candle power. photo metrical (fō-to-met'ri-kal), a. [ Gr. φῶς (φωτ-), light, + E. magnetism.] The photometrically (fo-to-met'ri-kal-i), adv. As [ relation of magnetism to light. Faraday. photomechanical (fōtō-mē-kan'i-kal), a. Gr. φῶς (φωτ-), light, + E. mechanical.] Pertaining to or consisting in the mechanical production of pictures by the aid of light, as in photoengraving, photolithography, etc. Of all the perfected photomechanical proce es, the col The Engineer , LXVI. 279. lotype is about the most useful for general purposes. photo met allograph (foto-me-tal'ō-graf), n. [ photometer (fo-tom'e-ter), n. [ F.photomètre = Sp. fotómetro = Pg. photo metro = It. foto me tro, IMG:content-0066.png:[merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small] a, balance by which weight of candles burned in a given time is de termined; b, candles; g, clock, and meter which measures the gas consumed in the test; / gas-burner; 4, flexible pipes for supplying gas to the burner; d, sight-box, supported on a carriage s; e, scale regards photometry; by means of a photometer. photo metrician (fo" "tō-me-trish'an), tō-me-trish'a n. [ The best way for a photometrist to be certain of his instruments is to test them himself. W. R. Bowditch , Coal Gas, iii. 67. [= F. photomé photometry (fo-tom'et-ri), trie = Sp. fotometría = It. foto me tri a, nation. See photometer. photomicrograph (fo-to-mikro-gråf), n. [ photo micrographer (foto-mi-krog'ra-fèr), n. [ photomicrographic (fō-to-mi-krō-graf'ik), a. [ appara + din photomicrography; photomicrography hotomicrography (foto-mi-krog'ra-fi), n. [= F. pho tom i crog rap hie; microphotography. photo nephograph prices having a guide way for the carriage of the sight-box, and graduated having intensity equal to that of the candles. This graduation corresponds with the position of the sight-box when the latter is adjusted so that equal intensity is obtained on both sides of the disk; is a curtain to exclude other light during the adjustment of the sight-box; i, cord running over pulleys under the bottom of the instrument, by which an operator can start or stop the clock at the beginning and end of the test;, disk, with the translucent serrated spot 7,; m, sight tube; o o', mirrors. Light enters the sight-box from the candles through the opening q in the side of the sight-box, and from the gas burner on the side of n. Images of both sides of the illuminated disk are simultaneously seen at n n' by reflection from the mirrors at o and o'. at which the light from two sources produces equal intensities of illumination. One of the most common photom eters is that of Bunsen, which consists of a screen of white paper with a grease-spot in its center. The lights to be compared are placed on opposite sides of this screen, and their distances are so adjusted that the grease-spot appears neither brighter nor darker than the rest of the paper, from whichever side it is viewed. When the distances have not been correctly adjusted, the grease-spot will appear darker than the rest of the paper when viewed from the side on which the illumination is most intense, and lighter than the rest of the paper when viewed from the other side. The intensities of the two lights are to one another as the squares of the distances from the screen at which they must be placed in order that the grease-spot may appear neither brighter nor darker than the rest of the paper. Another form is Rumford's photometer, which employs a screen in front of which is placed a vertical rod; the positions of the sources of light are so adjusted that the two shadows which they cast are sensibly equal. - Dispersion photometer, a form of photometer by means of which the intensity of a brilliant light, as that of an electric arc, may be determined. The dispersive effect of a thin concave lens acts like increase of distance in the common photometer to weaken the bright light to the required degree. - Polarization photometer, an instrument in which the measurement depends upon the properties of polarized light. Wedge photometer, an astronomical photometer in which a wedge of neutral , n . oh (fō-to-nef'ō-graf), [ write.] A name given by Abney to an apparatus for taking simultaneous photographs of a cloud from two points on the earth. It consists e entially of twin cameras, adjustable at any angle of elevation and azimuth, and, as used at Kew, England, placed 200 yards apart. Two sets of photographs are taken simultaneously at an interval of about a minute, and from these the heights and motions of the clouds are deduced. photo nephoscope (fo-to-nef'ō-skōp), n. [ pho top a pyrography (fō-to-pap-i-rogʻra-fi), n. [