Yellow Naphthol

Orange-yellow powder. Soluble in water. Used principally for making ray filters.

Narrow-Angle Lens - III, 289. (See Angle, Narrow.)


The term applied to the metallic silver image on a glass plate or film in which the lights and darks of the original appear in reversed order. From the negative a positive may be printed, which again reverses the order of high-lights and shadows and gives a correct reproduction of the original. Negative Collodion. (See Collodion.)

Negative Lens

(See Lens, Negative.)

Negative Paper

(See Paper, Negative.)

Negative Varnish

A varnish used for protecting the film side of the negative from scratches, etc. (See Varnish, Negative.)

Doctoring Negatives

Manipulating a negative either during development or before printing, so as to get better results on the print. When doctored just before printing the work is usually done on the back of the negative. Opaque and semi-opaque substances are employed to retard printing on certain parts, while ground-glass substitute is sometimes flowed on the glass side and this made transparent over sections that require deep printing, etc. Negatives, Drying - I; II.

The drying of negatives can be hastened by first draining the plate after washing, then placing them in alcohol or formalin for a minute, or less, then setting the negatives in a draft, where they will dry quickly.

Reversed Negatives

Negatives in which the image is reversed with reference to right and left.

Stripping Negatives

(See Acid Hydrofluoric.)


A trade name for papers manufactured by Eastman Kodak Co,

Nitrate of Ammonia

(See Ammonium Nitrate.)

Nitrate of Iron

(See Ferric Nitrate.)

Nitrate of Silver

(See Silver Nitrate.)

Nitrate of Uranium

(See Uranium Nitrate.)


A name applied to potassium nitrate, also sometimes to sodium nitrate. The former, however, is usually designated as saltpetre, while the latter is more frequently termed nitre.

Nitric Acid

(See Acid Nitrate.)

Nitro-Hydrochloric Acid. (See Aqua Regia.)

Nodal Point

An optical term designating, respectively, the points of admission and emission on the axis of the lens where all instant or emitted rays converge to a point.

Non-Abrasion Developer

A developer containing a very small percentage 5 grains to the ounce of solution - of iodide of potassium. This chemical acts in such a way as to keep the whites of the print clear and free from black lines or abrasion marks.


A term applied to the rays of light which have practically no chemical action upon sensitive substances.

Normal Developer

A developer that is properly balanced; i. e., a developer that has not been modified in any way for under or over-exposure, but compounded for the treatment of a normally exposed plate.