MOVING PICTURES IN COLOUR.

Auckland Star, Volume LXIII, Issue 161, 9 July 1932, Page 3 (Supplement)

MOVING PICTURES IN COLOUR.

HOW THE SCIENTISTS HELPED. Before explaining liuw moving pictures <-an be shown in colour you should be quite dear on the way scionee solves the mystery of colour. Among the profound and useful discoveries of Isaac Newton was one that ordinary light becomes a band of colours when it. strikes a glass prism. These colours begin with red at the bottom band, then orange, yellow, green, blue and violet at the top. Why do objects have different colours? Why is grass green, a geranium red, a tumbler blue, a horse white? The best answer we can give is that an object wo call red can absorb all the rest of the colour from light except the red. When it comes to transparent coloured things,-such as red wine or blue glass-r----and this is important for our talk— the colour we see depends on how many of tliu six colours are absorbed, and which colour passes through it. It is said that a white surface is one from which ali colours are reflected with the same strength that they are received, and a black surface is one which has absorbed all the colours and reflects none. The white light which turned to colours when Newton held up the prism can be combined into white light again by allowing the colours to strike a large cylindrical lens, which will then throw u spot of ordinary light on a screen. A later discovery of great value in colour photography was that only three colours were necessary to produce all other colours. These three colours, red, green and vioSft-Llue, are called the primary colours. This knowledge is used to give the effect of daylight on the stage by using a, row of footlights with the bulbs alternately coloured red, green and violet-blue. If three .photographs are taken through transparent materials of these colours and made into slides, they call be placed exactly one above the other, and when shown on a screen every colour of the original is produced. It may seem easy to take three photographs of a stationary object, but how was it to be done for moving pictures, taking three from exactly the same position? The first attempt was to take two pictures in the otic machine, using first». red, then a blue-green screen. The film was put in a special camera which turned at double speed, and every alternate picture was taken through these colours. Special projectors, also running at double speed, and with red and green windows revolving in front, were used to throw the pictures on the screen. This was called the kinemacolour.

In another idea, the Patheeolour, great patience, was needed, as it meant tinting by hand each black and white picture on the film. Technicolour, the process used in the picture "The Broadway Melody," is the one most often seen. After the light passes- through the lens of the movie camera half is passed through a bluegreen screen, and the other half through a red-orango screen, and then to (lie film. Thus, two photographs are taken each time, and one is upside down. The two pictures are printed on top of each other by a very clover method. The negative—the film exposed in the machine —is placed against the blank positive film, and moved downwards to print one lic-d-ornnge picture to each two negative pictures; a second positive film is placed against the negative, which moves upwards this time and prints the blue-green pictures. These two films are now cemented together in a machine so that they tit exactly over each other, and are then put in the developer. It is then toned iu chemicals by being floated on a solution in a sixfoot trough. An English company has a method of putting three colours on the same side of the. films, called the zocchroine method. A camera with four lenses is used, three being much smaller than the fourth. Three screens, red, green and violet-blue, are behind the small lenses, each, of these colour-screen photographs is one-quarter the size of the ordinary picture him. The fourth picture

is plain black and white; it is on this that the three coloured images are built. In printing the negative on to a positive film the black and white is printed first; it is then developed, and when dry recoated with the light-sensitive emulsion. The first colour picture negative is then enlarged before being printed on to the black and white picture. The film is again recoated, and another colour image enlarged on to it, and the same process repeated for the last. Thus we can get a picture in colour on the screen through the transparent colours en the film.