Intensity Ratio

The relation of the diameter of the aperture of the lens to its focal length. The focal length divided by the diameter of the stop equals the intensity ratio.

Invisible Image

(See Image, Latent.)

Iodide of Ammonium

(See Ammonium Iodide.)

Iodide of Cadmium

(See Cadmium Iodide.)

Iodide of Potassium

(See Potassium Iodide.)

Iodide of Silver

(See Silver Iodide.)


Bluish-black friable plates; metallic luster; peculiar odor; sharp acrid taste. Soluble in a solution of potassium iodide; carbon disulphide; chloroform. Use: Vapor of iodine was employed as a sensitizer by Daguerre for his silver plates. In combination with other compounds iodine is used in sensitive emulsions.

Tincture of Iodine

Made by dissolving iodine in alcohol. Used to remove stains of silver nitrate, first touching the stains with tincture of iodine and then with potassium cyanide or hypo.



A metal of a grayish, luster-like color. Use: Various salts of iron are used in photography, especially in the iron printing processes, such as blue-print process (ferro-prussiate), the platinum process, etc. The word ferrous or ferric is often used in place of the word iron. The ferrous salts contain more oxygen than the ferric.

Iron Ammonium Citrate

(See Ferric Ammonium Citrate.)

Iron Chloride

(See Ferric Chloride.)

Iron in Water

Iron Nitrate

(See Ferric Nitrate.)

Iron Oxalate

(See Ferrous Oxalate.)

Iron Perchloride

(See Ferric Chloride.)

Iron Sulphate

(See Ferrous Sulphate.)


A term applied to sensitive emulsions which are prepared to render correctly relative color values. (See Orthochromatic.)

Japan Varnish

An asphaltum varnish

Javelle Water

(See Eau de Javelle.)

Jena Glass

(See Glass, Jena.)

Jew's Pitch

(See Asphaltum.)

Kallitype Process

A printing process quite popular, especially among amateur photographers. Similar in principle to platinum printing process. The action of light changes the ferric oxalate to ferrous oxalate and the latter salt when in solution reduces the silver nitrate to metallic silver, resulting in bluish-black or black images.

Kilo or Kilogramme

A metric measure of weight


A trade name used by the Eastman Kodak Company and applied to both the box and folding cameras made by that concern.


A varnish composed chiefly of shellac dissolved in alcohol, colored with dragon's blood, gamboge, etc.


There are various forms of lamps used in photography for dark-room illumination. In all cases, however, it is essential that the light, in order to be perfectly safe for handling sensitive plates, consist of a deep ruby as well as an orange glass or similar material, either paper or cloth, which will give identical results.