# Bauhaus-Universität Weimar

### Volltext Optic Projection: Principles, Installation and Use of the Magic Lantern, Projection Microscope, Reflecting Lantern, Moving Picture Machine

Titel:
Optic Projection: Principles, Installation and Use of the Magic Lantern, Projection Microscope, Reflecting Lantern, Moving Picture Machine
Person:
Gage, Henry Simon and Henry Phelps Gage
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit39438/622/
6i4
EFFECT OF APERTURE IN PROJECTION
[Ch. XIV
Consider a sphere of one meter radius having this lighted surface at its
center. The light received by one square meter of the surface of this sphere
will then be B cos 0 lumens. Only half of the sphere can receive light from
this opaque surface and the entire light received by this hemisphere will be:
sin20 d20
= vB
Now if the reflecting surface is perfectly white there wall be no light lost and
the entire light received by the hemisphere will equal the light incident upon
the reflecting surface, that is iB = 1/10,000 and B = i/io,ooo*- candle-
power per square centimeter. In the above example where the incident
illumination is 48,000 meter candles, the surface considered as a source of
light will have 48,000 candle power per square centimeter.
IO.OOOT
This same formula will apply to the case of opaque projection (§ 274a) where
it is desired to determine the ratio of the light getting through the objective to
form the screen image and the light falling on the opaque surface, assuming that
this opaque surface is perfectly diffusing and perfectly white. In the case of
the objective, light over a certain zone of the hemisphere is used. If the angle
which the objective subtends with a point on the object taken as the center is
called 20, then the angle between the axis and the edge of the objective is 0,
and the above formula will apply, i. e., the light flux striking the objective
from one square centimeter is vB/2 (1 — cos 20). Also the total light flux
reflected from the surface over the entire hemisphere is irB, hence the ratio of
the light flux striking the objective to form the screen image to the light flux
received by the reflecting surface is 1—cos 20. This takes no account of losses
2
due to reflection and absorption by the objective.
* l2r

### Nutzerhinweis

Sehr geehrte Benutzer,

aufgrund der aktuellen Entwicklungen in der Webtechnologie, die im Goobi viewer verwendet wird, unterstützt die Software den von Ihnen verwendeten Browser nicht mehr.

Bitte benutzen Sie einen der folgenden Browser, um diese Seite korrekt darstellen zu können.

Vielen Dank für Ihr Verständnis.