We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
CH. X] PHOTOGRAPHY AND PROJECTION 381
For the occasional use of a laboratory the stray light can be excluded by means of asbestos paper. Sometimes the arc lamp is put on the outside of a partition, but that necessitates going out of the printing room to adjust the lamp. If direct current is available an automatic lamp is a great convenience.
PHOTOGRAPHING WITH PROJECTION APPARATUS
§ 541. Apparatus which will give good projection of microscopic specimens can, with slight modifications be used for photomicrography.
There are three possibilities:
(1) Printing the image directly on a developing paper.
(2) Exposing a dry plate directly to the image as for the paper.
(3) Using a camera and plate holder.
§ 542. Printing the projected image directly on a developing paper. — With the apparatus set up exactly as for drawing one can expose a sheet of developing paper to the sharply focused image of the specimen as described for the enlargement of negatives (§532). The lights and shades will be reversed, but all the outlines and details will be present. This is a convenient method of getting an enlarged record of the specimen.
It is also a good method for making pictures for models (§ 511) especially when there are many details. With the cheap developing papers in rolls now obtainable the expense is not greater than for making drawings, and there is liable to be a gain in accuracy. The main draw-back is that but a single picture is made of each specimen for a single exposure, while in drawing it is as easy to make two or three as one, by using carbon paper (§ 511).
§ 543. Exposing a dry plate directly to the image. — A dry plate may be exposed as just described for the developing paper. The object must be so placed on the stage of the microscope that the image on the screen will be a mirror image of the specimen, that is, the rights and lefts will be reversed as they should be in a negative. The image is sharply focused, and the light cut off with a deep red glass so that the plate will not be affected.