Lampblack

A fine carbon formed by the condensation of the smoke of burning oil, pitch, or resinous substance, in a chimney terminating in a cone of cloth. Lampblack is a basis for the majority of black ink colors, and as it is permanent is used in the carbon process.

Flash Lamp

Flashlamps are of various forms and construction, the most important of which are thoroughly described in the text.

Landscape Lens

(See Lens, Landscape.)

Optical Lantern

(See Optical Lantern.)

Lantern Plates

(See Plates, Lantern.)

Lantern-Slides

(See Plates, Lantern.)

Lantern-Slides, Coloring - V, 1007-1028.

Latent Image

(See Image, Latent.)

Latitude of Exposure

(See Exposure, Latitude of.)

Oil of Lavender

A volatile oil. Used in photo-mechanical processes chiefly as a solvent for asphaltum. A solvent for pyroxylin, also employed in shellac varnishes as a solvent for the shellac.

Lead

Pb.

A bluish-gray, soft metal. Soluble in nitric acid. Useful for lining wooden sinks. Hypo will not affect it. Lead forms several salts, some of which have photographic uses.

Lead Acetate

Pb(CH3COO)2 + 3H2O. Acetate of Lead, Sugar of Lead. Efflorescent, colorless, shiny, transparent crystals; sweet metallic taste; highly poisonous. Employed in toning baths and sometimes as a hypo eliminator.

Lead Chromate

PbCrO4.

Chromate of Lead or Chrome Yellow. Brownish-black lumps or brown powder. Soluble in acids. Used in opaques and paints as a coloring material.

Lead Nitrate

PbN2O6.

Nitrate of Lead, or Plumbic Nitrate.

White, translucent crystals. Soluble in water. Used with potassium ferricyanide as a negative intensifier.

Lead Toning

Acetate of lead is sometimes used in a toning bath for silver printing-out papers, but as its permanancy is questionable its use is not recommended.

Blacking for Leather

VI. (See Varnish.)

Cement for Leather

Dissolve guttapercha in carbon disulphide, having it of a syrupy consistency. Use hot.

Length of Focus

(See Focus Equivalent.)

Lens

A transparent body generally made of glass, having surfaces either spherical or plane, constructed for the purpose of concentrating or scattering rays of light. The various forms of construction are fully treated of in the text.

Achromatic Lens

Achromatic means destitute of color. An achromatic lens is one composed of two or more glasses, which so control the color rays of light as to bring them to the same focal point as the visual rays of light.

Aplanatic A lens free from astigmatism. (See Astigmatism.) Lens

A lens practically free from spherical and chromatic aberration when used at a large aperture.

Apochromatic Lens

A lens constructed for use in three-color work and color photography, being free from chromatic aberration.