International photographer (Jan-Dec 1941)

Notes on Optimal Pick-Up Design; H. G. Baerwald, Brush Development Co., Cleveland, Ohio. A complete analysis is given of a class of distortions arising in the reproduction of lateral-cut disk recordings. These are due to the varying angular deviation between the direction of the pivotal axis of the pick-up stylus and the groove tangent, commonly referred to as "tracking error." As long as the overall distortion present in the reproduction is moderate, the system is "almost linear," and it is permissible to superpose the different components of distortion. This permits separate treatment of the tracking error distortions. In the simple case of a sinusoidal signal, the complete Fourier spectrum of the pick-up signal is obtained. For general signals, an explicit analytical expansion is obtained for the picked-up signal. The kinematical effect of the tracking error is an alternating advance and delay of the pickedup signal with respect to the recorded one. The harmonic distortions may thus be characterized as side-bands of phase modulation of the signal by itself. Compared with the ordinary type of non-linear distortion as, e. g., met in tubes, which can be correspondingly characterized as amplified auto-modulation, the spectral distribution of the tracking error distortions is different by emphasis on the higher frequency components. For the second-order distortion, which is the prevalent type, this emphasis is proportional to frequency. The analysis shows that the distortions due to tracking error are considerably greater than commonly assumed, regarding both their absolute and their nuisance value. Some values given in the literature are more than 50 per cent too small, due to the omission of rigorous procedure. The recording characteristic does not affect the relation between ordinary type and tracking distortions. The distortion is given approximately by the weighted tracking error which is inversely proportional to the grove radius, and is referred to the mean groove radius of the record. The pick-up design should reduce the weighted tracking error as much as possible. The optimal design is uniquely determined as soon as the type of approximation is prescribed. It is argued that the Tschebychew approximation, which is commonly used in the design of electric wave-filters, is also adequate for the present case. For pickups without offset angle, only second-order approximation is possible, while with the right value of offset angle, third order approximation becomes possible. In the first case, sufficiently small values of distortion can barely be obtained with conventional arm lengths, and in order to avoid unnecessary distortions, the pick-up should be care fully mounted to obtain the optimal underhang. With an offset arm, distortion can easily be reduced to negligible magnitude. The right mounting is again fairly critical, while the optimal offset angle is not. Simple design formulas of immediate applicability are developed covering the whole practical field of record sizes, speeds, and arm lengths, and the effect of deviations from the optimum designs is given. The magnitude of the centripetal effect in offset arms is also investigated. Judith Anderson in "Lady Scarface" Judith Anderson, whose brilliant work in "Rebecca" made her a nominee for the Academy Award to the best supporting actress of 1940, has been signed by RKORadio Pictures to play the title role in "Lady Scarface," which has just gone into production with Dennis O'Keefe and Frances Neal in the romantic leads. Cliff Reid is producing, with Frank Woodruff handling the megaphone. I like tNeim short By Ralph Stauh Short subjects, long the stepchild of the motion picture industry, are coming into their own. Not only are they getting unprecedented shooting schedules, player value and story consideration, but ace cinematographers are being assigned to short subject units to insure their continued excellence. Here's a little inside information on the new set-up in the short subject field which should prove illuminating to those men and women whose time is engaged in making movies. When a man is allowed to spend 30 days making a one reel film where previously he had been compelled to get eight reels of film in the can in eight days or less, he is pretty happy to continue making shorts. That's why I like them short. When I started making short subjects, almost a decade ago, I was a one-man operation, producer, director, cameraman, actor and often the off-stage voice which explained sequences in the picture. Now, back with Columbia as producer of the Screen Snapshots, I have the pick of competent men and women in all specialized fields of movie-making to work with. I left the Columbia short subject department to head a similar unit at Warner Brothers primarily because I had ambitions to become a feature picture director. That ambition was later realized, but sweating blood to get 8,000 or more feet of film completed in less than eight days doesn't come under the heading of recreation. So I'm back at Columbia, with my own unit, most of the biggest stars in the business to work with and thirty days to make a picture which will run 10 minutes on the screen. Naturally I like short subjects. They not only provided me with my start in this business, but they also taught me just about everything that can be learned about the motion picture industry. It looks as if shorts are going to occupy an increasingly important place in the cinema sun. Not only are they testing grounds for stars, or experimental laboratories for technical improvements in all fields of the movie industry, but they are getting longer runs, increased attention from theater men. The shorts are probably important to every specialized unit in a studio. They provide cameramen with opportunities of testing innovations; they give directors a chance to test new theories and the allow little known players an occasion for trying their wings. I like them short. Ralph Staub "A Yank in the R.A.F." Betty Grable. who has been climbing the movie ladder at a fast clip in recent months, will co-star with Tyrone Power in "A Yank in the R. A. F." which Darryl F. Zanuck will produce for 20th CenturyFox as one of his costliest films of the year. Henry King will direct the film under the associate producership of Lou Edelman. The British Air Ministry, the R.A.F. and the British Air Commission are cooperating with Zanuck and some of the footage will be shot by R.A.F. pilots over Germany, France and England. Gene Tierney Gets Title Role in "Belle Starr" Gene Tierney, acclaimed by critics as one of Hollywood's most promising young actresses, was selected by Darrvl F. Zanuck to play the title role in "Belle Starr," drama of the most colorful feminine outlaw in history, which 20th Century-Fox will film in Technicolor. This culminates a search which has held back production for a year, during which forty-seven actresses were tested. Her selection follows close upon her fine performance as El lie May in "Tobacco Road." The importance of "Belle Starr," in which she will share honors with Randolph Scott, is expected by the studio to raise her to stardom in her own right. International Photographer for May, 1941 19