The Library of Congress Inner Workings

Carol Galbraith, the motion picture laboratory specialist in film inspection at the Library of Congress, took me on a tour through the film preparation area. This section of the Library of Congress complex is responsible for the inspection, cleaning and repair of film. Films are carefully inspected over light-boxes on work benches and any damage is noted and repaired. The repairs can vary from a single perforation replacement to a major repair of missing frame sections. The repaired film is then cleaned in an ultrasonic film cleaner and then goes to the timing/grading area.

A film with severe perforation damage

An example of the type of damage the film preparation area repair.


Film perforations being cut into repair type

Film perforations being cut into repair tape.


The term timing and grading refers to the process of determining exposure values for film to be printed so as to produce a final result of good density.  It is known as 'timing’ in the USA and 'grading’ in Europe and Australia. Currently the Library of Congress work on black & white film only but do have the capability to go colour in the future.

Ken Kuban demonstrated the timing or grading process of motion picture film to me. This process involves a visual bench check of the film for its physical condition before it is placed onto the film analyser.  The film is wound over a light-box and the sprocket holes and splices are checked along with the overall condition of the film.

A man checking the condition of a film on a winding bench

Ken Kuban checking film over the work bench.


Once checked the film moves on to the analyser. The analyser is calibrated to a known standard and the film is then laced in place. As the film is run through the analyser a video image is generated on a screen that allows the operator to view the film in its positive form. The operator can then adjust the density of the image using the analyser controls and record these values. This information is then transferred to the printing machine where the values are used to control the amount of light used to make the final exposures onto the copy film.

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