Society of Motion Picture Engineers : incorporation and by-laws (1916)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




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.

FRESNEL LENS Absorption Coefficient 1.3% per cm. Distanceof Loss in % by ab Sum Loss in zone center of zone from opt. axis Loss in % by reflection on surface sorption and length of path in lens in (mm) of losses % I 2 (10. 0) 7-1 4-3 4-1 1.2 (10. 0) 9-7 I . I 22.0 4.8 4-5 1 .2 (lo.o) 10.5 2.8 29.8 6.0 4-5 1.2 (10. 0) II. 7 3-3 37.6 9.0 4-5 1 .2 14-7 5-0 Total Loss Absorption Coefficient 3.9% per cm. 12.2% Distanceof center of zone from opt. axis Loss in % by reflection on surface Loss in % by absorption and length of path in lens in (mm) Sum of losses % Loss in zone I 2 (10. 0) 7-1 4-3 3-9 3-8 (10. 0) 12.0 1-4 22.0 4.8 4-3 3-S (lo.o) 12.8 3-4 29.8 6.0 4-3 3-7 (lo.o) 14.0 3-9 37-1 9.0 4-3 3.6 16.9 5-8 Total Loss 14.5% Loss of light on a concave silvered glass mirror as used behind the light source is caused (a) By the reflection of the in and out going ray on the outside surface, which amounts to about 8%, (b) By reflection on the silver film, which varies considerably with the quality of silvering, 10% being an average figure, and (c) By the absorption in the glass which amounts to from 1% to 4% for a mirror of 5 mm. thickness. These figures add up to a total loss of about 20% on the mirror. If photometric measurements show in general a greater loss up to 50% in commercial mirrors, the reason may be found in most cases in the poor silvering and bad conditions of the surfaces. In the case of a double condenser about 73% to 80% of the light contained in the angle 2u reaches the image of the source after having passed through the condenser. Of the 80% which in the best case is reflected by the spherical mirror, 20% to 27% are lost by passing the condenser so that the total amount which reaches the image of the source equals in the best case 80% -j 64%, or 1.44 times the amount contained in the angle 2u. If the higher figure for the loss in the condenser is taken, the total is reduced to 73% + 58% or 1.3 1. 56