International projectionist (Jan-Dec 1951)

Tv Viewing Difficulty Corrected by B. & L's Tele-Ban By BAUSCH & LOMB OPTICAL COMPANY NOT so long ago ophthalmologists and optometrists began to notice that an increasing number of patients complained of "difficulty" in viewing television. The severity of this trouble, as reported, ranged anywhere from a sensation of tiredness after several hours of viewing to an inability to tolerate more than a few minutes of watching. Examinations revealed that many needed corrective lenses. Many others, however, were already adequately corrected or did not require prescription changes. These latter patients posed a new problem. A specific solution, to be prescribed for patient relief, remained to be determined. Sense and Nonsense Some professional people arranged Tvset experiments at home to ferret out the probable cause of their patients' complaints. Various tinted lenses were tested, including several sunglass types. Rules for Tv viewers to follow appeared in papers and periodicals, along with news stories about Tv. Some of the printed material was sound, and some was ridiculous. Soon we began to receive inquiries as to what we might offer as an answer to the dilemma. Our answer is the new television glass, Tele-Ban, developed specifically for relief of discomfort in Tv viewing, and for giving he wearer crisp, sharp pictures. X and Gamma Ray Tests It should be understood, at the outset, that Tv is not dangerous to the eyes. There are no X and gamma-ray radiations evident when tested, over a 40-hour period, with health film in contact with the kinescope tube face, and with voltages up to 12 Kv. Discomfort, rather, is compounded of several factors including (a) the energy distribution of the source, (b) too short an observation distance, (c) lack of surround illumination, (d) the chromatic aberration of the eye. One might look at the energy distribution of the kinescope tube, see its similarity to the energy distribution of a daylight fluorescent lamp, and conclude that no cause for investigation existed. But this would not take into account the fact that the daylight lamp illuminates what we see by reflected (and therefore altered) light, whereas we view the kinescope tube directly. As far back as 1888, Konig and Brodhun studied brightness discrimination at scotopic levels (adjusted to see in a dark environment) , and demonstrated higher sensitivity for short-wave light. Crozier and Holway, in 1939, studied brightness discrimination at photopic levels (adjusted to see in a bright environment) , in several sizes of test field, with chromatic illuminations, and from their data one can extract the information that sensitivity is highest in the blue, with green and white second, and red the lowest. The separation for sensitivity levels for blue, green and red is substantial. Hence, the kinescope tube high level of energy at about 440m/u (blue) is important, after all. It is responsible for the high energy level in the area where the brightness sensitivity of the eye is greatest. IA-IP Radio Hams Constitute Theater Tv Talent Backlog By AMOS KANAGA (W6BAA) Sec. L. 419, San Mateo, Calif. Activity on the ham bands has been at an all-time low except for the 75-meter phone band which still sparks out with the midnight wisecracks from the boys down South and up around Montana. We often wonder if that years'-old checker game of two IA guys who are well known to the hams will ever be wound up, to the intense disappointment of the dozens of BCL listeners who kibitz right along with them. Becoming ever more popular with the boys is 75 and 10 mobile. Could this be the reason why a lot of fellows are leaving for work earlier than usual? Of great importance, we think, to radio hams everywhere is the announcement by President Walsh of the IA's intention ot doing a thorough organizing job on the Tv field. For our part, we do not know of a gang more qualified for Tv work than are the radio hams — those technically-qualified men from the IA-IP amateur radio list. Nice Backlog of Tv Talent Most certainly there is experience in the electronic field on that list that, with just a little more schooling, could be used to the great advantage of the craft. Perhaps we could profit by going back over those issues of IP which presented basic data anent Tv. After all, the fundamentals of Tv remain pretty much the same, and I doubt whether anybody knowing these fundamentals would have any great trouble in handling any form of theater Tv. Many thanks to the boys for their many nice letters, and we do try to answer all of them. Keep the suggestions coming. An up-to-date list of IA-IP hams appears in this issue. 73. Viewing Distance Important Too. many Tv viewers feel that they see the picture better if they hug the screen — one to six feet away. When at an observation distance of about five feet, the short-wave light (blue) and longwave light (red) are about equally out of focus (because of chromatic aberration), with energy in the blue predominating. (At greater distances the blue is more out of focus.) This fact is recognized and is commonly used in the theater to create a soft, out-of-focus effect by illuminating the scene with blue spotlights. Hence, again, the excess energy in the shortwave portion of the visible spectrum is a source of difficulty. It does not take much imagination, at this point, to guess that a reduction in the energy in the short-wave part of the spectrum should effectively halt complaint. But, how to do it? Available filters either do not absorb enough, in the right places, or absorb too much. Those that absorb too little do not do the job. Filters that absorb too much, such as Kalichrome C, are harsh; they distort colors, and are worthless for colored Tv. The criterion — absorption of the proper amount of blue with minimum absorption elsewhere — had to be met by a new filter. After several months of fruitless work with colored glass with proper optical characteristics and additional time spent on coated lenses the solution, in TeleBan, was found. Tele-Ban lenses are coated. They are stable. The coating is permanent and as hard as the glass itself. St mi-finished Tele-Ban lenses can be finished in the prescription shop, with no more than normal precaution against scratching. Tele-Ban is unique and is unlike other selective absorptive lenses. It is designed specifically for the job. Tele-Ban assures comfortable Tv viewing. The effectiveness of Tele-Bans has been amply demonstrated by field tests and by an intensive user survey. Reports have been enthusiastic: Tele-Bans definitely make Tv viewing more comfortable. When people complain about difficulties in viewing Tv, apart from those produced by ametropia (erroneous refraction of the eye, causing imperfect vision), one can be sure of obtaining relief by the use of Tele-Bans. They will be available generally later this year. Seager in Ansco Sales Post Charles W. Seager has been named Eastern Manager of Ansco's professional motion picture sales department, with headquarters in the Chrysler Building, N. Y. City. Seager joined Ansco in 1946, following an extended tour of duty as a Major in the U. S. Signal Corps during World War II. Previously he had been identified with the visual education field. INTERNATIONAL PROJECTIONIST • August 1951 25