DEFECTS IN NEGATIVES AND PRINTS 511 



3A. Prevention. — Determining and removing the cause of light obstruction. A 

 common source of trouble by beginners in photography is that of placing their fingers 

 in front of the lens, thereby obstructing light from part of the desired image. Improp- 

 erly folded bellows may sometimes cut off light from edges of negative. 



4A. Remedy.— 'None. 



IB. Distinguishing Characteristic— Irregular streaks. 



2B. Cause!. — Prevention of uniform development of the negative. Sometimes this 

 may be caused by oil or grease from the fingers which prevents action by the developer. 

 If the negative is washed in water before developing, especially in cold water, certain 

 areas which are resistant to the action of the developer may be produced in 

 the washing. 



SB. Prevention. — If due to oil or grease, cleanliness and systematic habits in proc- 

 essing will prevent recurrences of this defect. If due to washing prior to development 

 (such washing is of much assistance in preventing the formation of air bells during 

 development), the wash water should be at the same temperature as the other process- 

 ing solutions, preferably between 60 and 70°F. 



4B. Remedy. — Probably none if due to grease. If due to resistant areas set up by 

 wash water, local intensification may be useful. 



IC Distinguishing Characteristics. — ^Light area on negative appearing as (a) a 

 smudge or (b) generally approximately circular with irregular, sharply defined edges. 



2C Cause. — Sodium thiosulphite coming in contact with negative before develop- 

 ment. In (a) the hypo is transferred to the negative by hypo-stained fingers, whereas 

 in (6) the hypo appears to have been splashed on the negative. 



ZC. Prevention. — Cleanliness and careful habits in developing. Do not permit 

 unprotected negatives to lie around the darkroom where they may be subjected to 

 contamination. 



4C Remedy. — ^Local intensification may sometimes be found useful. 



Static Lines and Markings. 



1. Distinguishing Characteristics. — Dark spots with diffused edges singly or in 

 combination with thin, dark, irregular, forked or branched wavy lines. Static mark- 

 ings have been classified by Crabtree and Ives as follows: (a) small black spots with 

 diffused edges similar to certain types of moisture spots or spots caused by chemical 

 dust; (b) black spots with radiating branches; (c) treelike markings; (d) fan-shaped 

 markings; and (e) combinations of dots, branches, and fans. 



2. Cause. — These marks are caused by static electrical charges accumulating 

 on the uegative. The charges may accumulate within the camera, during processing, 

 or in handling the dry film. In the case of rolled motion-picture film, reeling or imreel- 

 ing the film during cold, dry weather may produce appreciable static. A common 

 source of camera static is that in which the negatives in film packs or roll films slide 

 over a velvet protected corner or through a light trap. 



3. Prevention. — Camera static may be prevented by removing all sources of friction 

 between the film and the camera and by making all parts of the camera of electrically 

 conducting material so far as this is possible. Winding the roll film slowly, or pulling 

 through an exposed film in film packs very slowly, will help diminish the formation 

 of static charges on the film. Since static is most easily formed with dry substances, 

 rehumidifying the film, especially if motion-picture reel, will tend to diminish forma- 

 tion of static. Conducting the combustion products of an alcohol lamp into the 

 camera chamber is also given as a method of prevention by Crabtree and Ives. In the 

 case of motion-picture processing, static produced in the laboratoiy processing niaj- 

 be discharged by passing the film through tinsel or tin foil playing over both surfaces 



