Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . (Photograph \ S] a monochromatic reproduction of a colour effect grades onecolour into the next by a mere or less abrupt change from lightto dark. Nobody can say exactly how dark a certain patchought to be in order to give effect to the colour of an object, andthis depends on the fact that the effect of a colour on the eye isby no means the same thing as the chemical effect of the colouron the sensitive emulsion. It we consider the Suns spectrum those co
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . (Photograph \ S] a monochromatic reproduction of a colour effect grades onecolour into the next by a mere or less abrupt change from lightto dark. Nobody can say exactly how dark a certain patchought to be in order to give effect to the colour of an object, andthis depends on the fact that the effect of a colour on the eye isby no means the same thing as the chemical effect of the colouron the sensitive emulsion. It we consider the Suns spectrum those colours appear to usto be the brightest which are nearest the red end of the scale. BALLOON PHOTOGRAPHY. 299 Red and yellow seem bright; green, blue and violet seem muchduller. But on a photographic plate the reverse is the blue and violet rays have the greatest actinic effect, thered ones have the least. Consequently the print shows blue aswhite and red as black ; at least, it has this tendency, and thetransformation actually takes place in extreme cases. Thus thechemical effect of the various rays of the spectrum on the photo-. Fig. ISO.—Photograph of a. village, taken in daylight by the Vega Company, ofGeneva. It should be compared with the similar photograph taken by thelight of a projector on the next page. graphic plate is altogether different from the physiologicalimpression produced on the eye. Even if the colouring of thelandscape does not appear to correspond to any particular colourof the spectrum, but to be made up of a number of components,each with its own peculiar physiological effect, the photographicreproduction will show a totally different grading. The brightyellow will still appear darker than it ought to be, and the darkblue will produce somewhat of the effect of white. This effect is exaggerated in balloon photography. The blue 300 AIRSHIPS PAST AND PRESENT. rays are more largely absorbed by the air than the others, andtherefore all bright objects
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
