This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Exposure. The exposure required in making the portrait for this illustration with the rheostat on its second point, was 2 seconds with a Portrait Unar lens, full opening.
Rembrandt Lighting With Aristo Lamp. In making our Illustration No. 78 of Rembrandt Lighting, we placed the subject a little closer to the source of light, with the camera stationed on the shadow side of the subject. The diffusing screen was exactly the same as for Plain Lighting except that the tan curtains on the end of the screen farthest from the subject, were slightly drawn to prevent the light spreading too far over the face. The reflecting screen was placed closer to the subject in order to carry the light around the face and illuminate the shadows. For exact positions of diffusing screen, reflecting screen and subject, background and camera, see drawings of floor plan (Illustration No. 79).
Exposure. As Shadow Lightings require a trifle longer exposure than Plain Broad Lightings, the exposure given in making this illustration was 3 seconds with full opening of lens.
Use Of The Rheostat Or Controller. The rheostat or controller furnished with the Aristo Lamp is a device for increasing the volume of light. This device acts as a resistance to the current as furnished from the outside to the lamp. There are different stations indicated on the rheostat, each supplying a different amount of resistance. At Station No. 1 the lamp is normal; at No. 2, a little of the resistance has been removed and a stronger light given; at No. 3 a still stronger light is given; No. 4 grows still stronger, and No. 5 removes all resistance and full lighting capacity of the lamp is given.
579. It is advisable for focusing work, and until you are ready to make the exposure, to place the rheostat at normal, and when you are about to make the exposure turn the crank to the different stations, carefully and slowly, from one station to the other. For adults, station 2 or 3 is sufficient; for children the highest station should be used.
580. After the exposure is made, the crank on the rheostat should be returned to its normal station before the current is shut off. Make it a practice to always have this crank at normal when you are through with your sitting. In this way you save your instrument, as well as your current.