Things differ very much in reflecting power; white chalk reflects about 90% of the light falling upon it, snow about 80%, an ordinary brick wall will reflect perhaps 20%, black printing ink less than 10%, while the blackest thing we can get, like black velvet, will reflect only 1% or 2% of the light falling on it. The ratio of the greatest brightness reflected in any scene to the lowest brightness may be referred to as the "scale of contrast" of the scene, so that if we have white chalk reflecting 90% of the light and have to photograph it with black velvet in the picture reflecting only 1% of the light and they are both lighted from the same source, then the scale of contrast will be 90 to 1.

Artura Iris Print, From Eastman Portrait Film Negative.

Artura Iris Print, From Eastman Portrait Film Negative.

Middle Atlantic States Convention Demonstration By W. B. Poynter, Cincinnati, Ohio.

A scale of contrast in which the highest light is only four times as bright as the deepest shadow is considered low, and photographic subjects having this scale would be called very flat. A scale of 10 to 1 is a very soft contrast; a scale of 20 to 1 is a soft contrast; and a subject having a scale of 40 to 1 would be a subject of normal contrast.

Natural subjects like landscapes differ very much in contrast. We have taken some pictures of different landscapes when we carried with us a photometer, an instrument for measuring brightness, with a little standard lamp. We measured the brightness of natural subjects and found that the flattest subjects - scenes at the lake and on the shore - would have contrasts as low as 1 to 5, while the strongest contrasts we get, from the shadow inside a wood to sunlit hills outside over the river gave us a total difference of brightness of 1 to 250, the sky outside being 250 times as bright as the deepest shadow inside the wood.

In studio work the contrast is governed largely by the character of the lighting. It was, for example, found by actual measurement that the contrast range between a white waist and a black skirt on a sitter, when the lighting was of average quality, was 1 to 40, while the same subject under a softer lighting gave a contrast range reading of 1 to 30. In line lighting the contrast range obviously may be very great indeed.

In general, in home portraiture, it is difficult to keep the contrast range low and at the same time secure lightings pleasing from an artistic standpoint. Measurement showed that typical cases gave a range of 1 to 65 on the sitter. When rather dark room furnishings form the background, the contrast between, say, a sitter's waist near the window and the darkest portion of the background may easily be 1 to 100.

We see then that in regard to brightness photographic subjects differ in two respects: They differ in regard to the total average illumination falling upon them and they differ with regard to the contrast of brightnesses which occur in the subject, which it is the business of the photographic process to translate into the black and white of the print. The total brightness is of importance because if the total brightness is low, we shall have to give the light more time to act on the photographic material than if it were high, but nevertheless, whatever the total brightness, if the contrast range is the same, we shall get the same result if we give the correct exposure. (To be continued.)

Artura Iris Print, From Eastman Portrait Film Negative.

Artura Iris Print, From Eastman Portrait Film Negative.

Middle Atlantic States Convention Demonstration By W. B. Poynter, Cincinnati, Ohio.