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.
shadows have been eliminated in arc projection.
In conclusion, emphasis should be placed upon the use of proper carbon combinations. The carbon manufacturer specifies a definite diameter of carbon for a definite current requirement and any deviation from this will result in poor projection. If the projectionist is without positive knowledge of the amount of power he is using he can obtain this by means of a voltmeter and ammeter. Standard instruments for this purpose can generally be obtained from the local power plants.
Discussion
In reply to some questions as to the relative efficiency of direct current and alternating current arcs, Mr. Ward said that it took about twice as much power with an A. C. arc to produce the same screen illumination as with D. C. With a small metal coated negative, the arc is steadier and is from lo to 15 percent more efficient.
Mr. Mott contributed some remarks concerning the new white ffame, A. C. carbon. The white flame material in A. C. carbon gives 10 to 15 percent, more candlepower, and since the light is whiter, the acuity is greater. The Navy Department made tests showing that the spectrum of the white flame carbon arc more nearly resembles daylight than neutral arcs.
The crater is hotter and there is more light in the arc stream, owing to the vapor from the white ffame material which fills in the time and form deficiencies of the wave form. For this reason the stroboscopic effect is lessened; this white ffame arc has the further advantage of being comparatively noiseless.
Mr. Kunzmann said that accurate data is available regarding the proper sized carbons to use under different conditions, and, as this is the secret of good projection, there is no reason why any projectionist should use the wrong trim.
28