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.
234 RICHARDSON'S BLVEBOOK OP PROJECTION
The difference may be observed by tracing on paper the outline of the two types and then measuring the depth of the effective beam at the point where the shutter is located. Shutter blades should be variously trimmed to cut the varying beam depths most effectively.
Effective Beam
(96) All light not falling upon the aperture opening is of no importance. The rear shutter master blade does not begin to cut light until its edge passes a straight line drawn from the top of the converging element to the top of the aperture opening — or from the bottom of the aperture opening to the bottom of the converging element provided the shutter runs in the opposite direction and starts cutting from below.
We have therefore coined the term "effective beam," this being the beam of light incident in whole upon the projector aperture. It may be defined as a cone of light bounded by straight lines drawn from the outer, free, diameter of the converging element (mirror or lens) to corresponding points upon the projector aperture opening.
Projector manufacturers hold this definition to be correct, but declare that the effective beam is bounded by straight lines reaching from the projector aperture opening to a rectangle on the face of the converging element, the same shape as the projector aperture, but so large that each of its corners would touch the converger's free diameter edge.
This statement is incorrect when we discover that in some measure a round beam of light can be put through a rectangular opening. This may be proven by painting a converger (mirror or lens) writh opaque water color and making a pin hole at its free diameter edge. Upon trial it will be found that a thin cone of light will go forward, some portion of which will always fall upon the aperture opening. It will be found by making other pin holes nearer the center of the converger that more of the spot light made by the cone will reach the aperture opening, until finally, near the center, it is likely