510 HANDBOOK OF PHOTOGRAPHY 



ID. Distinguishing Characteristic. — Dark or opaque streaks, often reasonably 

 straight, with fairly sharp edges; sometimes accompanied by general fogging of the 

 negative. 



2D. Cause. — ^Light striking and fogging the plate or film, (o) If the edges of 

 the negative are clear (transparent), fogging is indicated as having taken place within 

 the camera, (b) If the entire negative is fogged, fogging may have taken place in the 

 darkroom, while loading the negative material into the camera, or at any other point 

 at which the entire negative may have been exposed to radiations, (c) Certain resin- 

 ous woods, varnishes, composition slides, etc., have also been known to produce irregu- 

 lar streaks or blotches or fog. 



3D. Prevention.— DeteTvaination of the cause of the streaks or fog will usually 

 suggest suitable remedy, (a) Pinholes in the camera bellows, old and faulty film or 

 plateholders, and improper insertion of the slide in the plateholder are frequently 

 responsible for this type of defect. The slide should not be inserted in the film holder 

 by one corner, as this opens the velvet light trap and permits fogging. The entire 

 edge of the slide should be inserted all at once, (b) Handle negatives, especially the 

 sensitive panchromatic emulsions, in complete darkness or in a safe light which has 

 been proved to be safe for the type of emulsions used. Use changing bag, if necessarj^, 

 when loading negatives into their holders. Exclude all light (and other radiations 

 such as X ray, ultraviolet, infrared, and undue heat) from the darkroom during proc- 

 essing, (c) Airing the camera, plateholder, or other offending and fog-producing 

 apparatus in fresh air and exposing it to sunlight has sometimes been found helpful. 

 Painting the interior of the metal and wood parts of the camera with a weak solution of 

 bichloride of platinum is also useful. Change from composition to metal plate slides 

 is advantageous in some cases. 



4:D. Remedy. — General and local reduction may have some remedial effects. 



Dark Straight Lines. 



1. Distinguishing Characteristics. — Dark straight lines, starting from one edge 

 of dark portions of the negative (high lights) and running in one direction in a straight 

 Line away from the high light. 



2. Cause. — Insufficient agitation of the developing solution, permitting silver to 

 be deposited on the emulsion below the point where the greatest deposit of silver occurs 

 — the high lights. In motion-picture development, or in other processes in which 

 the film is continuously moved through the developing solution in a steady continuous 

 motion, this defect is caused by the fact that the first part of the film is acted upon 

 by fresh developer; later portions are acted on hy more or less exhausted developer. 



3. Prevention. — Agitation of the developing solution, or of the negative in the 

 developer. 



4. Remedy. — ^Local reduction of the negative, if carefully carried out, maj'' help. 



Fan-shaped Lines. — (See Static Markings, page 511.) 



Forked Lines Resembling Lightning.^ — (See Static Markings, page 511.) 



Light or Transparent Streaks or Blotches. 



As in the case of dark streaks or blotches, those which are transparent or lighter 

 than the mean density of the negative may have various shapes and may have poorly 

 or sharply defined edges. 



\A. Distinguishing Characteristics. — Light streak, sliarply defined or moderately 

 defined at edges. 



2 A. Cause. — Obstruction before the lens or in the camera between lens and nega- 

 tive which did not permit light to act on the negative. The more sharply defined the 

 streak is, the more hkely it is that the obstruction was close to the negative. 



