The Cine Technician (1935-1937)

36 The Journal of the Association of CineTechnicians Aug^.-Oct., 1936 Density Measurements of Release Prints CLIFTON CUTTLE (Kodak Research Laboratories) As a part of the program of the Projection Screen Brightness Committee, ^a number of density measurements of current release prints have been made. The purpose in the making of these measurements has been to supply data for the use of the Committee in its efforts to formulate a proposal for a standard of brightness. For this purpose, the data which appear to be significant are measurements of maxima and minima in density, a\'erage or total frame density, and density of the areas of principal interest. This latter density which has been named "Face Value" by Palmer^ will henceforth be referred to as "F" density. Apparatus and Data. Two distinct pieces of apparatus have been used in this work. Sensitometric interpretation of the data requires that maximum and minimum densities shall be determined with a standard diffuse densiometer. From such statistical data, it should be possible to answer the question of how much of the positive characteristic is being used by the laboratories in making release prints. From a knowledge of this fact, it will be possible to state definitely to what degree the laboratory can accommodate its product to the needs of the theatre. Use of the data by those dealing with the problem of screen brightness, from the point of view of physiological optics, requires that maximum, minimum, average, and "F" density values be determined under conditions which are effective in the theatre. For the first requisite, a standard Eastman circular wedge densitometer has been used. For the second set of values, a special "densitometer" shown in Figure 1 has been set up. In this instrument, an optical system commonly used in theatre projection has been copied as closely as possible. The dimensional data for the set-up are given on the figure. A concentrated filament light-source was substituted for the arc lamp customarily used in the theatre, because of the difficuties of density measurement with an arc. For convenience, the throw was shortened and the film-toobjective distance increased. The actual dimensions of the projected picture were reduced to 2' x 2' 8 1/2". In the plane of the projected image, a barrier-type photocell is located. The cell is movable in this plane so that any area of the picture can be selected for measurement. The sensitive area of the cell was diaphragmed to a 7T6 inch circular opening. Since the image magnification is about 40, the measured area corresponds to a circle of about 0.01 inch diameter on the film. Readings from a second cell so located that it can be placed over the lens to measure the total flux in the beam with and without the film in place is used to obtain the total density values. To provide a measurable image intensity witliout burning the film in the gate, required the insertion of a piece of TABLE I. Typical set of observations on miscellaneous release prints. -Maximum Face Average Scene Classifica Dmax Dmax Dmin Dmin Contrast Density Densit} Number. tion. Diffuse. Projection. Diffuse. Projection. Projection. Projection. Projection. 1 ICU 1-84 2-45 0-20 0-26 2-19 0-52 1-23 2 ILS 1-72 2-16 0-17 0-30 1-86 0-57 1-02 3 ES-CU 1-52 2-09 0-50 0-71 1-38 1-23 4 ICU 1-45 1-97 0-45 0-52 1-45 0-81 1-13 *5 ECU 1-86 2-54 0-78 0-95 1-59 1-08 1-68 6 IS-CU 2-09 2-65 0-65 0-76 1-89 M9 1-28 7 ES-CU 210 2-65 0-35 0-41 2-24 1-40 1-90 8 ES-CU 1-50 1-90 0-30 0-39 1-51 1-06 0-67 9 ILS 1-65 218 0-17 0-22 1-96 1-29 1-57 10 IS-CU 1-72 2-22 0-52 0-60 1-62 0-75 1-3S 11 IS-CU 2-02 2-64 0-15 0-18 2-46 0-94 0-99 12 IS-CU 1-66 214 0-20 0-26 1-88 0-62 MS 13 IS-CU 1-63 2-21 0-30 0-44 1-77 0-68 1-00 *14 ELS 1-72 2-34 0-40 0-60 1-74 — 1-36 15 IS-CU 1-52 215 0-30 0-30 1-76 0-71 0-95 16 IS-CU 1-53 2-04 0-23 0-35 1-69 0-81 0-87 17 ICU 1 -m 2-04 0-30 0-36 1-68 0-95 1-00 18 ICU 1-74 2-28 0-20 0-22 2-06 0-43 0-94 19 Title 1 -55 211 0-18 0-27 1-84 — M3 20 ICU 1-50 2-04 0-36 0-64 1-40 0-75 0-88 *21 ' ILS 210 2-57 0-50 1-05 1-52 1-40 1-64 22 ILS 1-70 2-30 0-35 0-43 1-87 — 1-66 23 ICU 2-10 2-52 0-45 0-52 2-00 1-60 116 24 IS-CU 1-52 2-10 0-30 0-37 1-73 0-95 1-09 25 ELS 1-72 2-22 0-25 0-40 1-82 0-57 0-95 26 ICU 1 -(iS 2-27 0-55 0-75 1-52 0-78 1-28 27 ICU 1-72 219 0-20 0-29 1-90 0-58 0-91 28 ICU 1-48 2-30 0-78 1-03 1-27 0-51 0-80 29 ICU 1-94 2-54 0-20 0-23 2-31 0-71 0-94 30 IS-CU 1-58 2-04 0-28 0-48 1-56 0-93 0-85 *Miglit Scenes (see opposite page).