The Bioscope (Jul-Sep 1931)

August 12, 1931 THE BIOSCOPE t Technical News and Notes Paris Illumination Innovations Our Editor, just returned from a Continental trip, gives me some interesting details of the remarkable illumination devices employed at the Colonial Exhibition, Paris, to which already upwards of ten million visitors have been attracted within the past three or four months (pity the local cinemas !) . I understand that apart from the general appeal which an exhibition of this kind is calculated to make to people of intelligence, there are certain features which of themselves deserve the special attention of theatre technicians who may be able to visit Paris during the extended run of the Exhibition. French artists have proved repeatedly that they are second to none in the improvisation of natural elements to achieve frankly artificial effects : Paris with its myriads of fountains provides countless examples of what I mean. But surely there has never been demonstrated a more powerfully effective use of simple colour lighting than that which is thrilling thousands of visitors to the Paris Exhibition night after night. Special coaching parties run in from miles around, just to view the illuminations only. Numerous fountains are colour flooded, the combination of spraying water effects and rapidly changing tints presenting a terrific spectacle. And the whole scheme has been executed on most economical lines, the absorption of light being reduced to a minimum, and the colour effects being correspondingly heightened to a maximum. Wood Which Looks Like Glass ^ hat seems to me to be of still more practical interest to the cinema lighting engineer, however, are the lighting units which line all the sidewalks throughout the Exhibition grounds. These take the form principally of standards about 12 ft. high, in designs of a more or less eccentric character. The base of each standard is artistically decorated— according to modern ideas of embellishment — and the actual lighting element occupies roughly a third of the space at the top of each standard. Viewed from a distance of from anything down to two °r three feet, these illuminants appear to be fitted with opalescent glass globes, through which a diffused but very positive light is shed. Actually there is not a scrap of glass , employed in any one of these street ” lights. They are simply of wood, painted white, the head of each standard being cunningly designed in shape to conceal tmy flood lights, which illuminate the whole surface of the painted wooden " globes ” One of the most effective of all the lighting pillars used in the Exhibition resembles a number of " trumpet *’ daffodils, arranged one m the other, about five or six tiers high Just inside the ” mouth ” of each trumpet are the floods, which throw a bright li°-ht in an upward direction, illuminating the one above it. It seems to me that this idea could be copied with a good deal of economy not only for exterior cinema lighting but for certain inside illuminants as well. I am told that until the closest inspection is carried out, there is nothing to arouse suspicions that these lights are not all they look. And there must obviously be a saving both in initial outlay— for glass is not too cheap as yet — and in maintenance. In any case cinema owners and technicians may find the possibilities worthy of their consideration. Saving On Light An American exhibitor was troubled by the size of his lighting bill— this is not a fairy story — so he set about cutting down the wattage used. He took care not to impair the efficiency of his lighting, yet he saved nearly 2,000 watts for several hours every day I This is what he did : — (1) Five 40watt lamps burning in the basement for safety purposes were reduced to 15 watts each. (2) Eliminated 30 lamps of 25 watts in front of the theatre. (3) Eight 25-watt lamps inside the theatre were eliminated at night after closing. (4) Twenty-five 10-watt lamps were eliminated until show opens. (5) Nineteen 25-watt lamps and eight 10-watt lamps in the balcony eliminated from 11 a.m. to 6 p.m. WHEN YOU WANT A CHANGE TO REAL GOOD WORK.' FOR HAND-PAINTED POSTERS, BANNERS, SHOWCARDS AND DISPLAYS OF QUALITY, TRY: CINEMA ADVERTISING SERVICE 6, MAIDEN LANE, LONDON, W.C.2. Telephone: TEMPLE BAR 5660. Let us quote you and be assured of prompt delivery and attention. These measures in no way detract from the theatre yet they effect a saving of 1,890 watts for several hours every day. Perhaps some similar moves in your theatre might effect a saving for you ? By Instalments A large firm of American general theatre and building contractors is offering to remodel theatres — from the " street to the rear door ’’ — on easy payment terms ! But what happens if your house wants overhauling again before you’ve finished paying for their first attentions ? A Loosely Used Term I am rather astonished at the loose manner in which the term " high intensity ” is applied to any and every type of projection arc-lamp— presumably as an indication of quality. When it first appeared, the H.I. arc presented such an advance on all existing lamps that it was naturally accepted as the " last word ” in projection illuminants. Since then there have been no developments of quite such a revolutionary character and, consequently, the H.I. arc is still looked upon with reverence. Good it most certainly is, but I am not disposed to believe that it possesses such marked superiority over some of the non-H.I. arcs which have recently been perfected as the frequent use of the term " high intensity ” to describe these new arcs would suggest. What H.I. Means High intensity is not a term referring to illumination — though this is the interpretation which many seem to put on it. A high intensity lamp is one in which the source of light is not the white-hot tips of the carbons themselves, but a small ball of incandescent gases which is formed at the crater of the positive carbon from the mineral salts with which the centre of that carbon is filled. If this ball of gases kept changing position, correct focussing of the light would be impossible. The only way in which the gas ball can be kept under control is to ensure that the positive carbon burns evenly. This can only be achieved by causing it to rotate on its own axis as it is fed forward. An H.I. arc is therefore — strictly speaking — one in which the positive carbon is automatically rotated on its own axis as it is fed forward. It is not an arc giving a high intensity illumination merely. Improvements Have Been Made1! Some exceedingly fine arc lamps have recently been produced, and it seems to me a pity that they should slavishly be referred to as " high intensity,” particularly as some of them at any rate present even a step forward on the straight H.I. lamp. I feel these arcs deserve a more original description. Who will supply one ? AC.