Bauhaus-Universität Weimar

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/lit39438/233/
225 
Ch. IX] MICRO-PROJECTION^ FOR LARGE CLASSES 
For a larger audience and a correspondingly larger room the 
screen distance might be made 15 to 20 meters (50 to 65 ft.), and 
the magnification raised from 250 at the lower limit up to about 
5,000 diameters at the upper limit. The smaller room enables 
one to get more brilliant screen images, and to use a wider range of 
objects (see table of magnifications § 391). In the smaller room 
the screen should be at least 4 meters (12-13 feet) square, and in 
the larger room 5-6 meters (15-20 feet) square. 
Fig. 123. Diagrams Showing the Construction of Objf.ctivf.s for 
Micro-Projection and for Photography. 
(From the Catalogues of Zeiss, Leitz, and the Bausch & Lomb Optical Co.). 
.•1 Microsummar of Leitz. 
B Microplanar of Zeiss. 
C Microtessar of the Bausch & Lomb Optical Co. 
When used for micro-projection the diaphragm is wide open anil no ocular is 
employed. 
In the diagram of the Microtessar, F represents the front lens, d the dia¬ 
phragm, and B the back combination of the objective. The arrow indicates 
the direction of the light. 
In articles and books upon projection, it is advocated sometimes, 
that oil or water immersion objectives as high as 1.5 or 2 mm. should 
be used for class demonstration. 
There is no doubt that brilliant images with short screen dis¬ 
tances can be obtained with high power objectives, but such pro¬ 
jection is only applicable for small numbers; and if fine details are 
to be seen, the observer must be very close to the screen. Further¬ 
more, no screen image in its finest details is equal to that which 
one gets in looking directly into a compound microscope. (For 
high power projection see § 401). 
If it is high magnification that is desired, it is vastly better to use 
lower objectives with an amplifier (§ 356, fig. 126). The lower
        

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