Grahame N's Web Pages

by Grahame Newnham BSc

The introduction of Kodachrome reversal colour film for the 16mm movie gauge in the USA during April 1935 and for 8mm in May 1936 and its subsequent launch in Europe, was somewhat of a set-back for the French Pathé 9.5mm home movie format in the mid 1930's. However within a year or so, Pathéscope in the UK were able to add the word 'COLOUR' in all their adverts, catalogues and house magazine when they began to distribute process paid Dufaycolor in special "H" film chargers for 9.5mm film makers. This would be the only colour film made available in the 9.5mm cine film size until Kodachrome in the early 1950's.

The seemingly simple process of using a black and white film with separate filters for the three primary colours had been proposed very early on in the history of photography by James Clark Maxwell, a British physicist. On 17th May 1861 he demonstrated that by using just three filters composed of the primary colours red, blue and green in special lanterns, all other colours could be created - the three colours together producing white light. Later he took three pictures of a tartan riband through primary colour filters. When the three photographs were projected using the appropriate filters and in accurate register, a passable colour image was achieved. Unfortunately because the photographic emulsion at the time had very poor overall colour sensitivity, the image produced was predominantly blue and there were problems achieving the essential accurate registration of the three images.

James Clark Maxwell's 1860's additive colour image

The use of three separate filters and photographic images was somewhat cumbersome even for still pictures. In 1895 Vidal suggested the idea of applying a series of coloured lines or squares to the film base. Various methods were tried including a random mosiac pattern system, developed by the Lumière company and marketed as Autochrome. However it was a French chemist Louis Dufay, (1874 - 1936), who invented a colour process using a tri-colour reseau filter, patented in 1908 and originally marketed for photographic plates in 1910 as Dioptichrome.The filter was achieved by ruling pairs of lines of complimentary colours such as magenta and green, placed at right angles to a series of non-complimentary colours, such as cyan and yellow. This produced a mosaic pattern of green lines interspersed with rows of red and green squares. This filter pattern was created on the film base with the light sensitive emulsion on top.

These methods of providing a reseau of tiny primary colours on the film base with the light sensitive (black and white) photographic emulsion coated over this filter layer, meant that the resulting film stock was exposed through the base of the film. After development, viewing or projecting through the film base provided a full colour image. This type of colour system is known as 'additive' as resultant colours are achieved by the addition of the primary colours. The main problems were that the reseau pattern, unless very fine, was visible to the eye when viewing the projected image; the actual image produced was relatively dim as light had to pass through these coloured filters; and the early film stocks were not very sensitive to the red and green end of the spectrum making a balanced colour image difficult.

Louis Dufay had discovered that a regular geometric pattern for the filters reduced the grainy appearance due to the 'clumping' of colour elements when a random colour filter dot system was employed. By the 1930's technical advances meant that a very much improved version of Dufay's system could be developed. Firstly an almost panchromatic (equally sensitive to all colours) film emulsion with higher sensitivity was evolving from the major film manufacturers. Secondly, vastly improved engineering standards enabled the rotary printing of very fine lines - fifteen lines to the millimetre had been the target, but by 1935 a colour filter screen having twenty three lines per millimetre had been achieved.

Dufay had marketed his process in various forms until the mid 1920's when his French company, Versicolor, set up to produce a movie film version of his process, ran into financial trouble. At the time a colour expert from the UK, T. Thorne-Baker had been working with Dufay, to report on the process to a British paper manufacturing firm, Spicers. As a result Spicers bought the process and in 1926 set up Spicer-Dufay in the UK. Research at the Spicer plant in Sawston, Cambridgeshire, continued, under the direction of T. Thorne-Baker, under total secrecy, for four years. Then in 1931, Dufaycolor was presented to the Royal Society in March and the British Kinematograph Society in September.

Dufaycolor 'reseau' colour filters - magnified about 150 times

The process had been considerably improved and modified by now, with red and green lines at 67 degrees to the frame and the blue at 23 degrees - this minimised the reseau visibility on projection. However reports at the time suggested that the diamond shapes were visible in a cinema from the first six rows or so. In addition the projected image was noticeably dim unless an improved light source was used; sound tracks were also quieter and because the film was laced with the base towards the lens, focussing of cameras and projectors had to be reset. However Spicer's investment of £500,000 enabled a 35mm cine film to be launched by the end of 1932. Soon the British photographic firm Ilford decided to invest in the company and the process. Spicer Dufay (British) Ltd was registered in February 1933 as a private company with a capital of £600,000. Ilford's main objective being the development of sub-standard movie film colour emulsions, particularly 16mm for the amateur market. The first 16mm Dufaycolor filmstock, together with an improved 35mm emulsion was presented at the Savoy Hotel in April 1934 and launched commercially in September with great success using the slogan "Dufaycolor: Everybody's Colour Film".

The Dufaycolor additive colour process was a reversal system that produced a viewing positive - this may have been suitable for home movies, but for the cinema multiple prints were required. Ilford who made the film stock for Dufay, devised a printing method for making 35mm positive projection prints from the positive originals. It was then used for a number of cinema shorts and for a couple of colour sequences in the film Radio Parade of 1935. Reviews suggested that out of doors and in close shots the performance of the Dufaycolor process was quite good, but studio work was still inadequate despite the quadrupling of the lighting. Soon, after further research, a conventional negative / positive printing system was introduced, using negative stock in the 35mm film cameras. A number of other short subjects were made for the cinema, costs being estimated at about four times that of black and white releases. Only one feature film was made in Dufaycolor - "Sons of the Sea" - made in 1939 and released in 1940. A copy I have on video looks very good - sharp and with good colours.

Optical sound tracks were printed directly onto the emulsion side of the filmstock using normal sound film printers using a red light which gave maximum penetration. Naturally on projection the Dufaycolor sound track image suffers some light and definition loss, but technical notes suggest about a 1.5db output level loss; described as 'negligible', this loss rising slightly above 3000 cycles/sec. The notes seem to suggest variable area sound tracks gave the best results. Tests had also been carried out on direct recording (through the reseau) on negative stock - quality was stated to be good enough for news films.

A newly formed Dufay-Chromex company launched the improved process in 1937 together with upgraded 35mm transparency and 16mm movie emulsions. By October 1937 Pathéscope in the UK announced in its house magazine The Pathéscope Monthly that Dufaycolor was now available in 9.5mm 'H' chargers, process paid, at a cost of 10/6d (approx 52p). As a comparison, a process paid "H" charger of PSPF black & white 9.5mm was 5/6d. In the November edition, the editorial included "All Colour 9.5mm Film - Of equal importance last month (they had announced the launch of the 'H' cine projector) was the last minute information that Dufaycolor in Pathéscope 'H' chargers was available. Autumn and winter provide very many occasions for taking films in colour and frequently the results may be found more pleasing than those obtained in the harder light of summer. Dufaycolor ensures the retention of natural tones that are so important in any colour process, while users will also find a long range of exposure allowing detail in the shadows. Why not try this all-colour film for your next exposure".

9.5 Dufaycolor from the late 1930's

The 9.5mm unexposed Dufaycolor sample I have, is packed in an all plastic "P" style charger, marked Dufaycolor, but also stamped Pathescope, and although marketed by Dufay-Chromex, it appears the film was made and processed by Ilford along with their black & white 9.5mm and 16mm movie emulsions. From examples remaining today, contemporary illustrations and reviews it appears the colours are reproduced reasonably well, but quite muted and pale. This is because if the coloured filters had been any more dense to provide saturated colours, the film sensitivity would have been considerably reduced and the resultant positive far too dense to project satisfactorily. (The 1980's ill-fated Polaroid Polavision Super 8mm additive colour instant movie system although giving good pictures via the special viewer was far too dense to project). For ninefivers Dufaycolor was restricted to those with decent (brighter) projectors like the 200B and the 'S' / 'Vox' designs.

9.5mm Dufaycolor "P" type film charger

Samples do still turn up today - I have one or two as returned from processing - either in the 30ft closed cassettes or as in the photo at the top of the page - on a metal spool marked 'Dufaycolor'; others are spliced into composite reels of 9.5mm film. Results look fine when screened with a bright light source (the Buckingham 9.5mm conversion for example) but the reseau pattern is visible, reminding one of the earlier LCD video projectors! There must have been a loss of sharpness when Dufaycolor was used in amateur cameras as the film emulsion was not in close contact with the front of the camera gate - the film was exposed through the base. There was also a danger of scratching from the rear presser plate or film guides, as these were designed for the film to run through the camera, emulsion side to the gate front.

As far as I can tell 9.5mm Dufaycolor disappeared with the second world war and didn't return. The 35mm slide film continued into the early 1950's - I remember around 1958, our school photography club bought slightly outdated 100ft lengths of 35mm Dufaycolor from a Liverpool firm - all that was left - and under the guidance of the biology teacher we experimented with reversal processing. Results from one batch were quite good, but I recall the second batch needed extra exposure and results were not so good. Presumably because manufacturing tolorances were poor, the 35mm film came with a batch code which indicated normal exposure, one stop under or over. If one ended up with the slower batch, it was difficult to get acceptable results except on a bright sunny day. These batch variations are strange, because the 9.5mm (and improved 16mm) film stock needed no extra filters or exposure variations. I find that Dufaycolor stock was around 8asa speed rating.

Naturally Dufaycolor was killed off by the more effective 'subtractive' colour systems, especially Kodachrome, which were rather more complicated to manufacture and process, but provided a much clearer, sharper and brighter image. This is the type of film we use today on 9.5mm - the Fuji Velvia, Provia and RTP artificial light emulsions which are much more sensitive, and give a superb, sharp, near perfect colour image.

It would be interesting to hear from anyone who used Dufaycolor, either professional or amateur 35mm transparency / 9.5mm / 16mm movie stock.

e-mail: gln @

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Paragraph on optical sound added 25May2010 - thanks Peter Ryde!