Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . nflowing water for another 10 minutes in the dark room. It isthen dried in a draught in the hot oven for about twenty minutes,but not more than twenty-five minutes. The solution can be usedfor a large number of plates; probably it is better to take halfthe above amounts, which ought to be sufficient for six or eightplates. The plates should be packed front to back, in whichcase they can be kept for months. The proper relative exposures for the red, green
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . nflowing water for another 10 minutes in the dark room. It isthen dried in a draught in the hot oven for about twenty minutes,but not more than twenty-five minutes. The solution can be usedfor a large number of plates; probably it is better to take halfthe above amounts, which ought to be sufficient for six or eightplates. The plates should be packed front to back, in whichcase they can be kept for months. The proper relative exposures for the red, green, and bluemust be adjusted by means of suitable stops. The filters usedby Miethe allow of stops of F/45, F/68, and F/15 for the red, 334 AIESHIPS PAST AND PEE SENT. green, and blue respectively. The speed of the shutter is arrangedto suit the prevailing light, and the camera is either held bymeans of a hand-strap, or is rested on the edge of the length of exposure may amount to one-tenth of a second,and it is therefore necessary to wait for a moment when there isno oscillation in order to make the exposure. In Northern lati-. FiG. 213.—Miethes camera for three-colour photography in a balloon. At the top is shown the front part with the three lenses, and below is seen the sliding screencarrier and the shutter. tudes, colour photography is only possible in a balloon when theweather is reasonably clear. The development of the negative is done in the usual way inthe dark room by means of a moderately concentrated solutionof rodinal, containing one part in nine of water. Towards theend of the development, the plate is examined on the back, andthe process is generally complete when the image begins to bevisible through the plate. A transparency is then prepared, and THE INTEEPEETATION OF PHOTOGBAPHS. 335 this is treated in the usual way hy Miethes three-colour project-ion apparatus, or the negative may be enlarged and printed onone of the three-colour photographic papers
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
