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Layers of Light- All the colours we see on film are made up by mixing red, blue and green light.  For example,
            green light and re{j light, when they overtap, will produce yellow light. Modem colour film-stock is made up of
            four parts.  In the middle of a strip of film is the 'base', which is simply there to provide a body tor the other
            components to be fiXed to.  This base is nonnally made of plastic.  Attached to one side of the base are tour
            emulsions- thin layers of light-sensitive chemicals.  One of these emulsions is specially made to be sensitive
            to blue light.  Another is green-sensitive, while a third is roo-sensitive.

            The other layer of emulsion, a yellow one, has a different job to do.  Instead of recording light, it blocks it.  It
            stops any blue light that may have got past the blue-sensitive layer from leaking in with the red and green light.
            Finally, there is a 'backing strip' on the other side of the base.  It is there to prevent any light that has passe{j
            through all the emulsions from bouncing back and destroying the clearness of the image.

            FILM and the CINEMA- The 1895 film show that marilad the birth of the 'movies' combinad the new invention
            of photography with the much older technique of projection.  People had been using projection for at least two
            hundred years.  It was basad on the principle that if an object is placed in front of a source of bright light, its
            image will be thrown forward onto a wall or screen.

            The use of projection had been very highly developad by the second half of the nineteenth century. Originally,
            ftlckering  candle light had been usad to  project the Image.  This was replaced by limelight, which was so
            Intense that it could project an image (usually a picture paintad onto a glass slide) from one end of a large
            public hall to the other.  The machine usad for this purpose was callad a 'magic lantern'. The Images on the
            screen could  be  ghostly, comical, spectacular. or a moral lesson teaching right and wrong.  Supernatural
            effects were sometimes obtainad by projecting the Image of a phantom not onto a screen, but onto smoke.
            This effect was made all the more Impressive when the magic lantern Itself was kept out of sight.

            Other subjects for  slide shows includad a man swallowing rats. a clown's perfonnance, a naval battle, making
            pottery, a fantasy voyage beyond the moon and an  illustrated lecture on the evils of alcohol.  Some of these
            shows made extremely skilful use of dissolves - that is, making one Image fade into another In quick succes-
            sion. These dissolves went some way towards creating the illusion of movement.  In a show about a famous
            tire In London, for example, the audience saw the smoke getting thicker and thicker, then the flames leaping
            higher and higher, and finally the fire dying down as the firemen's hoses playad jets of water onto it.

            The Challenge of Photography - At first, the slides use{j in magic lantern shows were hand-paintad.  Into a
            circular painting, about 3.51nches (90mm) In diameter. artists use{j to pack a vast amount of brightly-colourad
            detail.  The rigging on  a ship, the  leaves on  a tree, - all could clearty be seen on the screen, even when
            magnifiad forty times by a lens in the projector. By the 1880s, hand-painted slides were being challengad by
            photographic slides.  These were much cheaper to produce.

            THE MAGIC BOX - Though a camera has sometimes been callad a 'magic box', it is of course no more magi
            than a 'magic' lantern.  Both of them are basad on a scientific understanding of the nature of light. A French-
            man namad Nicephore Niepce was the first person ever to succead in taking a picture with a camera.  In 1826
            he use{j light-sensitive chemicals on a glass plate Inside a camera to fix an Image of two houses side by side.
            It took eight hours.

            Further developments in France and England soon raduced the necessary exposure tJme to between two and
            three seconds, in bright sunlight.  For sixty years, however, a glass plate, heavy and breakable, remalnad the
            only type of base available to photographers.  The exposure time, couplad with the weight and fragility of the
            equipment, meant that earty Victorian photography was much better suit ad to portraits and landscapes than it
            was at capturing anything in motion.

            The most notable exception to this was a photographer namad Edweard Muybridge.  In 1872 the Governor of
            California commissioned him to photograph his race horses galloping.  To settle a bet, he wanted  to know
            whether all four legs were off  the ground at any one point in time. After five years, Muybridge managad to solve
            the problem by placing a long row of cameras side by side on the edge of a race-track.  The shutter of each
            camera was connect ad to a piece of thread stretchad across the track. As the horse gallopad past, it broke the
            threads and so releasad the shutters of each of the cameras, producing glass-plate photographs taken split
            seconds apart.

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