According to specifications laid down by the Illuminating Engineering Society,[31] the minimum light requirement for average reading in the home is 20 footcandles of light. For fine print and sewing the minimum requirements are 35 to 50 footcandle intensity.
Standards for study and table lighting set up by this society, call for lamp bases 28 inches in height equipped with a reflector bowl made of opal diffusing glass, 8 inches in diameter. At a distance of 12 inches from the base of the lamp, a 100-watt bulb must give 30 footcandle intensity to comply with their standards, and at a distance of 36 inches, 5 footcandle intensity.
Divided into groups, utilitarian lamps fall into these classes:
Study lamps.—These are lamps which adhere to all of the I. E. S. standards and are used on desks for reading purposes or as a table lamp. They are somewhat less decorative than the regular living room lamp since they are more severe usually being made with a brass base and parchment or simple silk shade.
Table lamps.—These are decorative lamps with bases made from the same materials as the purely decorative lamps; however, they are usually more conservative than the purely decorative lamps, and rigidly avoid unusual shaped shades or novelty treatments which might cut down the utility of the lamp. I. E. S. standards are not rigidly followed on all table lamps, but the specifications serve as a master guide. When dark shades are used they are usually lined with white to reflect the light. Reflector bowls are used to encase the light bulb. These are made of holophane, milk, or glazed glass, and provide a diffused indirect light.
Commode lamps.—Commode lamps are smaller than table lamps and are usually used to flank a sofa or as pairs on either side of a chair grouping. I. E. S. standards for this type of lamp call for a base 23 inches in height, an 8-inch reflector bowl and an intensity of light, 12 inches from the center of the lamp, of 30 footcandles, when a 100-watt bulb is used.
Floor lamps.—Several types of floor lamps are now in use—the lamp with diffusing bowl and fabric shade and the reflector lamp. Floor lamps show a tendency to shorten and new junior floor lamps are about 10 inches shorter than standard models. I. E. S. standards on floor lamps call for a base 58 inches in height, a reflector bowl 8 inches in diameter and an intensity of light 12 inches from the base, of 30 footcandles, when a 100-watt bulb is used. At 24 inches from the base a 100-watt bulb should give 10 footcandles of light intensity, according to these standards. Floor lamps are usually made of metal or wood and many have marble or crystal inserts in the base. Many of the new floor lamps have three-way mogul-type lamp arrangements in addition to a reflector, which give four intensities of light. The reflector bowl may be lighted separately from the bulbs.
Reflector lamp.—The reflector lamp is a tall floor lamp with a glass or metal bowl. The light is reflected upward toward the ceiling. This is in contrast to the lamp with the diffused glass reflector bowl and fabric shade which directs the light downward toward the floor as well as throwing a portion of light toward the ceiling. The reflector lamp may be used instead of a ceiling light but is not recommended as a reading lamp.
Bridge or lounge-chair lamps.—Most of the old-type bridge lamps in which a bulb hung from a projected arm have been replaced by a reflector type lamp which employs a diffusing bowl. These bridge or swinging-arm lounge-chair lamps are smaller than the floor lamps, and can be adjusted to any position over a chair. Many have a cover or closed top on the diffusing bowl so the light will not shine in the user's eyes.