PHOTOGRAPHY.

Auckland Star, Volume XLIV, Issue 58, 8 March 1913, Page 15

PHOTOGRAPHY.

THE USE OF SODIUM SULPHITE. Although it is some thirty years ot so since Berkeley introduced l the use of sodium sulphite as a preservative, primarily with pyro, yet opinions are by no means unanimous as to how it acts as a preserver or stain preventer. One comfortable view is that it acts like a watch-dog and seizes upon the oxygen atoms (or molecules or ions) which are present in the water as "dissolved air," and so prevents them reaching the pyro or other reducing ("developing") agent. One practical point of considerable importance is the .outcome of experience, viz., that the quantity of sulphite should be proportional to the quantity of water used —say, logrs per oz. Thus, if a kotmal strength developer be diluted for stand or tank development, one should use a 15gr per oz solution of sulphite, and not plain water. We may reckon this as practically equal to loz of sulphite in li pint of water. HINTS ON HOME PORTRAITURE. Home portraiture, i.e., in living rooms rather than in a studio, with bhe usual convenience of window blinds-, changeable 'backgrounds, and 60 forth, is of more immediate interest to the average amateur. The three chief factors which should claim his attention seldom get sufficient, if any, attention at all, .writes Mr Lambert, 'F.R.P.S., in the "Daily Telegraph." First, there is the regulation of the window light in quantity by closing and' opening blinds or shutters, and in quality by the use of diffusing screens. For this purpose the cheapest white art muslin is excellent. It is convenient to make a light .bamboo cane frame, and fix bhe muslin to it by tapes, so that when soiled it can bo easily Tern oved and washed. The thinner, and 60 cheaper, this material the better it will serve its purpose. If the worker is obliged to use a window admitting direct sunlight a double thickness- may be required.

•Paradoxical as it may Beem, a diffusing screen which really stops a little of the right tends to shorten exposure. The reasoit is that with direct (unscreened) ligirt the great part of it falls on the side of the figure next the window, while the other side is in strong shadow. But with a diffusing screen the direct light is reduced-, while an appreciable quantity of light is scattered into the shadows, which are now lighter. And as exposures are for the most part based on the shadows, the exposures are thus reduced. It is a mistake to fix the diffuser close up to the-window, as the beginner is very apt to do, because we often require to screen only a part of the window. Also it is frequently desirable to graduate the light on the figure by placing the diffuser at an angle with the plane of the window.

In ordinary language the word "reflector" is often' used to denote a lookingglass or mirror. But in photographic portraiture such a Btrong reflector, as this is very seldom, if ever, desirable. Its use often leads to the effect known as cross-ligihting, suggesting two conflicting sources of illumination, -which is very seldom aecepta/ble. For portraiture it is infinitely preferable to use either white paper, card, or desirably a fabric on account of ite durability and washableness, if I may use the -term. i(A little starch ■helps to keep it clean.) Cotton sheeting 6ft wide-can be bought for about 1/6 peayard. A 6ft square reflector on a light framework serves admirably for all homework. The beginner frequently -errs by using the reflector (really a combined reflector and scatterer) too near the figure, so getting too much light on the shadow side. Tihere> should be only just enough reflected light to prevent the shadows looking hard and solid.. The professional background' often betrays its-eham character; the home•background of the beginner is usually a. -bewiWeriiig mass of detail or patchiness. The amateur may wisely rrfrain from bought •backgrounds, except, perhaps, a 7ft square of plain dark slate-grey. A -roll of dortble-'width dark brown thick paper used to underlay carpets makes an excellent background, and if a hand of thin black tape be sewn with half-inch stitches along the edges it will with reasonable care-laet; a- long time.