GB675479A - Colour cinematography - Google Patents

Abstract

675,479. Colour kinematography. MILLAIS, W. Nov. 12, 1948, No. 29460/48. Class 97 (i). Black-and-white negative colour selection records are formed on groups of successive film frames, the first of each group being exposed through two filters in succession, the second through two other filters and so on, all the filters being different and all passing the whole spectrum apart from one narrow region; a positive print is then made and each frame is projected successively through two filters passing wavelengths lying within the range transmitted by the filters through which the corresponding frame of the negative was exposed. In one embodiment, a shutter is used, during exposure, having four clear sectors in which filters, say A, B, C, D, are mounted and alternate frames are exposed respectively through A and B in succession and through C and D in succession. For projection, a shutter assembly as shown in Fig. 4 is used. The disc 42 has eight transparent spaces in four of which filters A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP> D<SP>1</SP> are mounted. The frames exposed through filters A and B are projected through A<SP>1</SP> and B<SP>1</SP> in succession, and those exposed through C and D are projected through C<SP>1</SP> and D<SP>1</SP>. Fig. 7 shows, against a scale of mÁ the absorption of the filters A, B, C, D at a, b, c, d. The masking and flicker blades of the projector are replaced by the disc 34 coupled to rotate with the disc 42. Clear spaces 35, 36, 37, 38 register with the filters in the disc 42. The spaces 39 contain violet filters which act as flicker shutters and the spaces 40, 41 contain colour filters, divided into differently-coloured sectors, the whole of each space being also covered by a grey filter. These combinations act as masking shutters. The whole filter assembly, intended for use particularly in a 35 mm. film projector, rotates once for each passage of two film frames. An assembly for 16 mm. film projection is shown in Fig. 6. The masking blade 46 is composed of coloured sectors backed by a grey filter, the flicker blade 48 being a violet filter. This shutter rotates once for each film frame, the filter disc 42 being driven at half this speed through reduction gearing 50.