A Manual Of Photography
Forfatter: Robert Hunt
År: 1853
Forlag: John Joseph Griffin & Co.
Sted: London
Udgave: 3
Sider: 370
UDK: 77.02 Hun
Third Edition, Enlarged
Illustrated by Numerous Engrabings
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164 SCIENTIFIC INVESTIGATIONS ON PHOTOGBAPHY.
above or under zero, at which the image seems best defined;
and after having removed from the camera the experiment frame,
and set the focus as usual on the ground glass, he has only to
move the tube of the object-glass by means of the rack and
pinion, and to push it in or out ; a space corresponding with the
division of the scale indicating the deviation of the true photo-
genic focus : the tube of the, object-glass is for that purpose
marked with the same scale of division.