Early Work In Photography
A Text-book For Beginners
Forfatter: W. Ethelbert Henry C. E., H. Snowden Ward
År: 1900
Forlag: Dawbarn and Ward, Limited
Sted: London
Udgave: 2
Sider: 103
UDK: IB 77.02/05 Hen
Illustrated with an actual negative and positive, and numerous
explanatory diagrams throughout the text
Søgning i bogen
Den bedste måde at søge i bogen er ved at downloade PDF'en og søge i den.
Derved får du fremhævet ordene visuelt direkte på billedet af siden.
Digitaliseret bog
Bogens tekst er maskinlæst, så der kan være en del fejl og mangler.
52 Early Work in Photography.
the ground glass occupies. The reason for this is the angle
at which the image falls upon the ground glass surface, and
in order to obtain an image more truly approximating what
the eye would see, we might have the ground glass curved,
as shewn by the dotted lines. But better still if we can
remove the candle to six inches, and the ground glass to six
inches from the pin-hole. This will give us the image in
the same relative position on the ground glass, and of (ap-
proximately) the same size, but in better proportion.
Suppose now, in place of the very small pin hole in a very
thin card, we take a hole one-eighth of an inch in diameter
in a card one-eighth of an inch thick. The rays from a
candle placed at A will pass through easily. If we remove
the candle to B only a small pencil of rays will pass through,
while by moving the candle to C, we prevent any rays from
passing through, because no straight line from C can pass
through the hole.
Fig. ro. Fig. Ii. Fig. 12.
If we now make the pin-hole considerably larger, say, a
quarter inch diameter, we shall find the image on the
ground glass much more brilliant, but much worse defined