Colour Sensitising Composite Portraiture
colour sensitometer has probably been a main factor in the recent extensive use made of the Du Hauron process for com-mercial purposes. A very full description of Abney's colour sensitometer will be found in The Amateur Photographer for July 19th and August 2nd, 1895.
Colour Sensitising. See Isochromatic Photography.
Colouring Photographs. An operation that requires con-siderable artistic skill and ability. Some useful details will be found in the article Bromide Paper.
Colours, Photography in. See Photography in Natural Colours.
Colour Triangle. See Triangle, Chromatic.
Combination of Printing Processes. Sometimes a print is commenced by one method and finished by another. Mr. Silberer, for example, prints in platinotype, and produces special effects by an over-printing in gum-bichromate. See Gum Bichromate.
Combination Printing. See Printing.
Combining of Lenses. See Amplifier, Adon and Lens.
Compensator, Miethe's. In using a wide-angle lens the falling off of the light from the centre towards the edges is often a serious inconvenience; but a many-armed star cut out of black paper and supported a distance behind the lens, will often prove a remedy. This star should be kept in rotation during a part of the exposure, and then removed. A neater device of a similar sort was suggested some years ago by Dr. Miethe. A plano-convex lens of tinted or M smoked " glass is cemented in a plano-concave lens, the combination being thus equivalent to a plain glass, the centre of which is more opaque than the edges.
Composite Portraiture. Mr. Francis Galton, by throwing faint images of a succession of accurately-adjusted prints (or negatives) on the same part of a single sensitised plate, has obtained resultant images which give a pictorial average of all the constituents. Racial characteristics are brought out in a remarkable way in the composite photograph. Particulars and