The Cine Technician (1953-1956)

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82 THE CINE-TECHNICIAN July, 1953 measurements and investigations which have been made since by the appropriate Technical Committee of the B.S.I., a new edition of the British Standard has now been published. This edition is more specific in regard to the value of screen luminance, which now has to lie within a specified range as measured on a horizontal axis both at the centre and sides of the screen, and as seen from any seat in the auditorium, and it also specifies a standard method of measurement. It is intended to be applicable to the type of screen with black masking which is in general use at the present time. This British Standard is now thought to be more comprehensive in its requirements than any of the corresponding standards issued by other countries. A new developer called Capitol has been put on the market by Johnsons of Hendon. The British Journal of Photography (12th June, 1953) carries an interesting report on it. Sensitometric tests with H.P.3 35mm. film revealed that even at the shortest developing time recommended for this film there was a speed increase of 2 degs. compared with D.23. Development time extended to 22 mins. produced a speed increase of 4 degs.; and a final test with a development time of 30 minutes gave an increase in speed of 6 degs., with a high though not impossible fog level of 0.57. A remarkable feature of this set of curves, pointed out by the author, was that as the development time was increased the contrast increased only slightly and the curves moved progressively farther and farther to the left. That is, increased development times give higher effective film speeds without increasing contrast beyond a reasonable figure. Incidentally, the instruction leaflet issued by the manufacturers points out that " the mere fact that acceptable negatives can be obtained by setting the meter at a higher rating than the manufacturer of the film recommends is no evidence that the developer has increased the effective speed." On which the author of the B.J. article has the comment : " This is in fact our old friend in need, the safety factor incorporated by the speed rating system." This picture, found m a film technician's pocket, from an unidentified illustrated journal, is dated December 1928. The caption reads: "A demonstration of the method by which the first lip-synchronised animated cartoon in the world is made. Mr. Joe Noble, who draws these cartoons for British Talking Pictures, is seen standing by the easel. It is quite remarkable to hear that, for once, in one branch of an industry dominated by U.S.A., Britain is first in the field." After the sensitometric tests referred to above, a series of exposures were made on H.P.3 roll film under low level lighting conditions of the order of 3 or 4 foot candles; assuming a rating of 42 degs. B.S. or 1,250 A.S.A., an exposure of l/25th sec. at f. 4.5 was given, and half the film developed in Capitol for recommended time of 30 mins. and half in D.23 for normal time of 16 mins. The latter portion showed complete lack of shadow detail but the portion developed in Capitol showed detail in all the shadows with a rather high fog level. Ten by eight prints from these negatives showed that the general quality did not appear to suffer in any way from the increased fog level. Graininess tests showed that for maximum speed ratings an enlargement of six times ought to be possible without too obtrusive grain, and at the normal rating for Capitol, the grain is the same as with D.23. The illustration, reproduced by kind permission nf the British Journal of Photography, shows n serit s of four characteristic curves for Ilford H.P.3 35mm. film, exposed in an Eastman lib sensitometer. As can be clearly seen when compared with D-23, a fine grain developer which gives normal film speed, Capitol, even at the shortest developing time recommended for this film, gives a speed increase of 2 degs.. and when the development time is extended to 22 mins. the speed increase becomes a total of 4 degs. 1 CAPITOL DEVELOPER • j lABO^LTO^r MST NO -sJf c B A yC— 0-25 RELATIVE LOG. E. Characteristic curves for Ilford H.P.:i 35mm. film developed m I >-!_*:{ and Capitol. Curve A is for Capitol at a dilution of 1+4 at 68 degrees F. for 11 minutes. Curve B is for Capitol at a dilution of 1 + 4 at 68 degrees F. for 22 minutes. Curve C is for Capitol at a dilution of 1+4 at 68 degrees F. for 30 minutes.