Dufaycolor, an additive colour transparency process, was named after M.Louis.Dufay, who manufactured Dufay Diopticolor and Dioptichrome Screen Plates in 1908.

Ilford Ltd acquired an interest in Dufay-Chromex Ltd. (14-16 Cockspur Street, London; later Dufay Ltd.) in 1935 for whom it started to manufacture a reversal colour film of the additive type under the brand name Dufaycolor. Dufaycolor had previously (from 1932) been available in England only as 16mm & 9.5mm ciné film, but Ilford's expertise and finance enabled it to be marketed for still photography in 35mm, roll, sheet and film pack forms.

Although processing was relatively simple (and instructions were published), Ilford offered a service for roll films. A 120 size roll film, for 6 exposures, cost 3s/4d (16.5p), over three times the cost of an 8 exposure b&w film and developing (to colour transparencies) cost another 1s/6d (7.5p). Hence, 6 Dufaycolor transparencies cost a total of 4/10d (24p), more than £10 in 2005 money.

Dufaycolor film had a speed rating of around 10ASA, a third of a conventional b&w film of the day. (Ref: Brian Coe, "Colour Photography, The first hundred years 1840-1940", page 72).

Dufaycolor film consisted of a transparent, non-inflammable base on which was printed a very fine transparent colour pattern consisting of alternating blue and green squares and red lines. This pattern was called the 'réseau' and the complete pattern of 3 colours was reproduced 20 to 23 times per mm. On top of the réseau was a coating of high sensitivity panchromatic emulsion.

The film was exposed through the base so that light passed through the colour réseau before reaching the emulsion. In this way the image was broken up into minute areas representing the red, green and blue components of the subject.

Alongside is a slide believed taken on Dufaycolor during the late 1940s, courtesy of David Muggleton. The image below shows a magnified area near the sitter's right eye, revealing the coloured réseau.

When a red object was photographed, the red light passed through the red areas of réseau but was blocked by the green and blue areas. Normal development therefore gave a minute black silver deposit behind each minute red filter element. These deposits were then bleached away and the film fully exposed to white light before being developed again. The previously unaffected areas of silver behind each of the minute blue and green filter elements were thus converted to black silver deposits, while the previously black areas behind the red filters, having already been bleached away, remained clear. After fixing and drying, the film was viewed by transmitted light, which passed through the clear areas, revealed the red colour that was in the original subject.

In July 1937 Ilford stopped marketing Dufaycolor (announcement in Miniature Camera Magazine) and the responsibility reverted to Dufay-Chromex Ltd of Elstree, Hertfordshire. At that time, Mr George H Sewell, ARPS (a well known amateur cinephotographer and author) was Sales Manager at Dufay.

The picture alongside is taken from the BJPA for 1937 at a time (pre-July 1937) when Ilford was still marketing Dufaycolor roll film, 35mm film & film packs (Type D.1) and flat film & 16mm cine (Type D.2).

"Dufaycolor is almost unlimited in its applications and unsurpassed for the quality of its results.

Dufaycolor is sensitized by Ilford Limited and sold and distributed by them in the British Empire, British Mandated Territories and Egypt."

See John Daly's site for more Dufaycolor information and useful links to others offering further information. Also some Dufaycolor examples taken about 1936 by John Daly's father, Melvin.

See my Ilford chronology for years 1935 and 1937 for further information.

In 'Miniature Camera Magazine' (MCM) for October 1937, p702, there is the picture alongside and a short article entitled "Colour on Tour".

"The picture shows an interested crowd around the Dufaycolor demonstration van. The van, equipped with the Marconiphone Public Address outfit has been creating great interest at Blackpool, and has been making a tour of the coast via Sunderland, Whitby, Scarborough, Hull, Grimsby, King's Lynn, Cromer, Great Yarmouth, Lowestoft, Harwich, Clacton-on-Sea to Southend for Carnival Week.

Paul Godfrey recognises the resort in the photograph as Gorleston-on-Sea a part of Great Yarmouth just up the coast from Lowestoft.

Later, the van will come back to Blackpool for the Illuminations Week with its operators ready to give advice and information to the thousands of users of Dufaycolor who will undoubtedly embrace this opportunity of obtaining colour photographs of unique character."

To the left is a Dufaycolor advertisement taken from Amateur Photographer for August 31st 1949.

Dufay also sold black & white Orthochromatic film, as shown in this November 'Photography' advert sponsoring photographic competitions during 1951.

A Lewis & Newcombe advert in AP for 21st December 1949 also lists 120 roll film Dufay black & white Panchromatic film, 4 for 11s/8d plus 6d postage, so effectively 3/- each roll (15p).

Its probable that these black & white films were both rebranded Ilford films.

120 Ilford Selochrome (orthochromatic) is priced in the same advert at 10s/4d for 4 plus 6d postage, so effectively 2s/8d each (13.5p).

"When you are viewing DUFAYCOLOR transparencies, either in the hand or with one of the accessories described above, you should stand facing the light. If you are indoors, face the window, approaching as close as is convenient.

See that the light reaching the reflector surface of the viewer is as white as possible. If you are viewing by artificial light the blue filter should be in position or the blue side of the reflector plate in operation.

The transparency is placed in position on the viewing platform and the device arranged to secure the maximum degree of reflection. If you are examining an original, the emulsion (dull) side should be towards you. If it is a copy, the emulsion faces away from you. If you are using artificial light, a table-lamp will provide a suitable light source.

Care should be taken to keep the reflector surfaces in the viewers clean and the lens in Model 'C' should also be kept free from dirt."

The viewing accessories are also mentioned in the publication, "The Dufaycolor Book", page 8 & Section IV.

The 60 page Dufaycolor Book, measuring 143mm by 221mm, was issued by Duafy-Chromex Ltd around April 1947, a third Post-War expanded edition, costing 3/- (15p). A book bearing this same title was available in 1937 from Dufay-Chromex priced 8p (3.5p), post free.

It describes in some detail the construction of Dufaycolor film, its exposure and reversal processing. An Amateur Photographer 31st January 1951 edition contains an advert (by Robinson & Sale, p16) for a Johnsons 'Dufay' Processsing Kit priced 10s/6d (52.5p).

There is also a section on producing colour prints by the preparation of tri-color Separation Negatives, followed by their printing and registration into a complete colour print using DUFAYTISSUE. The Dufaytissue consists of:

"A coating of coloured gelatine on a non-inflammable transparent film support, so compunded that it may be sensitised and developed and, after drying, transferred to a suitable gelatine coated white paper or card."

The three images are superimposed on white paper, so forming the finished colour print.

Another Dufaycolor book, this one positively identifying itself to Ilford Limited.

This copy belongs to Paul Godfrey who kindly supplied scans of three colour illustrations, see right and below.

The 10ASA speed of Dufaycolor film required lengthy exposures, as can be read in the text attaching to each picture.

Magazine entries in 1956, 1957 and 1960, seemingly chart the end of the commercial Dufaycolor process, though its quite probable some out-dated Dufaycolor was home processed for several years thereafter.

'Good Photography' magazine for March 1956 has a short paragraph in their 'Current News' column saying "35mm Dufaycolor is back after a two-year absence. The prices are: 12/- (60p) for a cassette, 9/- (45p) for a refill, 5/- (25p) for processing."

'Good Photography' magazine for August 1957 carries an advertisers announcement by F.E.Jones of 3 Breeze Hill, Liverpool, 9, saying "the Dufaycolor Factory has now ceased production and we have been favoured with the Disposal of the entire factory stock.
AT A FRACTION OF THE COST.
35mm 25 metre tins, 50s (£2.50p), 35mm 20exp. cassettes, 6s/6d (33p), 35mm 20exp. refills 5s (25p), 620 roll films (very limited) 5s (25p) and 127 roll films (very limited) 4s (20p).
ALL MATERIAL 1958 EXPIRY DATES, FRESH, TAX PAID, GUARANTEED.
Processing vouchers, price 5s, complete with address of recommended processing station.
Johnsons Dufaycolor Processing Outfit (sufficient for 4 films) price 12s/6d (63p).

The St.Annes Dufaycolor Processing Station, St Annes-on-Sea, had a letter published in the 'Readers Views' section of Amateur Photographer magazine dated 20th April 1960, saying:
"We intend continuing to process Dufaycolor at least until October of this year (1960) and then the position will be reviewed in the light of circumstances, although the probability is that we will extend the date of termination of processing until October 1961. After this date the quantity will have diminished sufficiently to no longer warrant commercial processing.
We have had many enquiries recently regarding the position, which we think, in the interests of all, should be made clear.
Our tests show the film still on offer to be quite good, although short-dated, but it is advised to open up half a stop on the recommended exposure for best results."