COLOUR PHOTOGRAPHY

New Zealand Times, Volume XXXVII, Issue 8330, 16 January 1913, Page 11

COLOUR PHOTOGRAPHY

NEW FLASH POWDER REDUCES EXPOSURE. As is known, the antochrome plates for taking photographs in direct colours were invented and first tried in Lyons. Important improvements in their use have been made there during the past year that are of interest to the photographer and to the general public. The reproduction of actual colours in a photograph has, until quite recently, says Mr Carl Bailey Hurst, United States Consul at Lyons, been attended with the greatest dill! culty, owing especially to the lack ot sensitiveness in antochrome plates in comparison with ordinary plates. This defect was a serious obstacle to the instantaneous work necessary in outdoor as well as in portrait photograpoy. Efforts to strengthen the sensitiveness of the autochromo plate by chang ing the emulsion resulted in destroying the fidelity ol the colours produced, but the problem appears to have been successfully solved in two ways: First, by substituting for natural light an artificial light strong enough to reduce the time of exposure to a fraction of a 'second. Second, by hypersensitizlng the plate, through the use ot certain colouring agents of the cyanide group., For the first method flash powders are employed as a source of light, notably, a so-called perchlora powder, which is a mixture of two parts ol magnesium and one part of perchlorate of potash. The substitution of this powder for the light of day has marked a new step in the production of a photograph’ in colour. The results are as favourable as those obtained in daylight, and the time of exposure can be regulated to a fraction of a second, since the quantity of light depends solely on the weight of the powder burned. In using this process the light entering the camera must be filtered through a screen different from that ordinarily employed in auto, chrome photography, and without it the colours reproduced under the agency of this powder would not be true to nature.