Motion Picture Herald (Oct-Dec 1951)

to a maximum of 10-15%. It is a reasonable condition, then, to try to maintain similar limits in apparent picture contrast during projection. In other words, a picture should not have more than 10% or 15% contrast change at the high than at the low limit of brightness level. Accompanying this article is a table which compares the brightness of the screen in foot-lamberts with the ability to see changes in contrast for various sections of a projected picture. Column A is the brightness of the center of the screen, with the projector running and no film in the gate. Column B shows the contrast effect if one looks at the high light of the picture only. Here there is only a 3% difference in contrast perception as the screen brightness is changed from 7 to 30 foot-lamberts. Column C shows the contrast effect if one looks only at the shadowed part of the picture. Here the perception in contrast varies from 0.33 to 0.50, or over 50% if the screen brightness is changed from 7 to 30 foot-lamberts. Column D shows the difference in contrast perception when looking at the area of the picture which shows the principal action or interest. Here the variation is from 0.75 to 0.98, or 30% if the screen brightness is changed from 7 to 30 footlamberts. Column E shows similar comparisons, but for an average brightness over the entire picture. Here the variation is from 0.69 to 0.94, or 35%. CONTRAST CONSISTENCY It can be seen, then, that the variation in projected picture contrast in all cases, except the high light areas, would be much greater than the margin permitted in the processing of release prints. If a picture were processed for a 10 foot-lambert screen brightness and be shown at 30 foot-lamberts, the picture element contrasts would be too great for good quality; and if the picture were processed for 30 foot-lamberts and be shown at a brightness of 7 foot-lamberts or less, almost all contrast would be lost and the picture would appear flat and dead. In order to prevent such wide swings of picture quality during projection, the original screen brightness standards recommended a mean brightness of 10 footlamberts, with a minimum of 7 and a maximum of 14 foot-lamberts. From the table we can see that these limits would just barely meet the permissible 15% variation of contrast change. In Column B the variation between 0.97 and 1.00 is 3%. In Column C the variation between 0.33 and 0.41 is 24%. In Column D the variation between 0.75 and 0.87 is 16%. {Continued on page 24) Theatre TV Demands Experience and Specialists -RCA SERVICE has both Only from RCA Service do you get the experience that comes from installing and maintaining more theatre TV systems than any other service organization — anywhere. Only from RCA Service do you get specialists trained in the television laboratories and factories of the pioneer in theatre TV. 4 ways RCA SERVICE can help you 1 Survey and help solve the special TV application problems relating to your theatre. 2 Supervise the installation, adjustment and testing of all video equipment, coaxial lines and antennas. 3 Give instruction and technical advice to your projection personnel in the efficient operation of the equipment. 4 Make periodic inspection checkupf . . . furnish replacement parts and tubes . . . supply emergency service — to forestall trouble, extend equipment life, keep repair costs down. It costs so little to protect so much And nowhere else do you get such specialized theatre TV service. Write for complete information. RCA SERVICE COMPANY, INC. A RADIO CORPORATION of AMERICA SUBSIDIARY CAMDEN, NEW JERSEY CYCLMMIC CUSTOM SCREEN GIVES YOU "CENTER SEAT VISION' From every seat in the house! Eliminates glare and distortion! . . . Gives amazing new depth! Perfect sound transmission! . . . No perforations! Manufactured by B. F. SHEARER COMPANY 2318 SECOND AVE. • SEATTLE, WASHINGTON . ELiot 8247 QKIT OISniBOTOI: nuua t HMSEN. UD.. 301 CUT STREU. SUN FRtHClSCO • UN«D«. DOMIHION SOUND EOUIPMENl. IID. • OFFICES IN PRINCIPIE CITIE3 BEHER THEATRES SECTION 23