PHOTOGRAPHIC.

South Canterbury Times, Issue 2897, 8 July 1882, Page 2

PHOTOGRAPHIC.

At a recent Thursday evening meeting of photographers in London, a question from the box was read : “ Why is gas of poor quality whenever the barometer is low ? This is asked with reference to the use of gas as a standard light for plate testing." Mr A. Haddon said that, although the gas might bo of the same quality, the light given out was less when burnt in low than in high pressure. Oxygen and hydrogen, which give, under ordinary circumstances, a flame with very little light, will bum with great luminosity when both are condensed. A screen covered with Balmain’s phosphorescent paint was. then set up, and a gentleman posed in profile in front of it. A few inches of magnesium wire were then burned in such a position as to throw the shadow of the sitter upon the screen. When the gentleman quitted his seat his shadow remained distinctly visible. The part of the background not screened by him glowed with characteristic phosphorescence. Several cameras which had previously beeu focused upon the screen were now 'uncapped, and exposures of five and ten minutes were given. On developing, distinct images were seen upon the screen, as well as upon those which had been exposed upon the sitter himself while the magnesium was burning.