Cueing and Printer Light Changes.
Cueing and Printer Light Changes Principles
In order to obtain a print that answers to the requirements of the customer or gives a faithful representation of the original copy or scene, the printed material has to be corrected scene by scene, in other words has to be graded. The estimation of the printing conditions needed to achieve this acceptable result is called Grading in English [but Timing in the USA].
All camera original film has been exposed to varying light levels which, however the cameraman attempts to control his camera exposure, results in variations in density from scene to scene.
Colour film has another dimension of variation in addition to that of exposure level as the illumination of the original scene varies in terms of the colour of the light. Light varies in its colour composition. Daylight has a far larger proportion of blue light than light from an incandescent electric light bulb. Daylight, too, is not constant in its colour composition and the light of a sunny day contains more red light than daylight on an overcast day. A colour negative therefore has variations in the proportion of red, green and blue information about the scene that depends on the lighting as well as the subject colours. In order to produce an acceptable visual result on printing some or all of this variation must be reduced to produce a subjective result that is acceptable from scene to scene.
Printer lights are the printing conditions needed to produce a graded print. Printer lights define the exposure required for the print and in the case of colour also refers to the filtration or other means of defining the colour of the printing light.
To ensure that, during printing, the printer lights required for each scene change at the right place [i.e. at the start of each scene] a signal, called a cue, is required to indicate that a change is required.
The print films used in the early days of motion pictures were slow speed and blue sensitive and quite bright safelights were used. The Kodak OB Safelight Filter over a 60-watt bulb was so bright that the operator could easily read his instructions and operate quite precise dial and levers. As film became more sensitive and especially as colour arrived, either no safelight or only a very dim brown light could be used. In consequence printing had to change to rely on equipment that could be pre-programmed to provide the cue and the new printer light in the dark.
Over the years, very many different cueing and light change methods have been invented. The three main and most used cueing methods are those that require some sort of physical marks or signals on the film that indicates when a change in printer light should occur and methods that count the number of frames from a start point to the change point. This last system is known as frame count cueing [or FCC].
The difficulty for an archive grader working in a laboratory where some or all of these machines are in use is that all the systems have different increments between light values. For example the Model D has an increment of 10%, so the each successive light gives 10% more exposure than the previous light. The Model C has an increment of 0.25 Log Exposure that means the amount of light doubles every 12 points. The Debrie system has an increment of sixth Root of 2, meaning the light doubled every six lights. The Lynes reduction printer has each resistance value adjustable so you could match it to any other printer.
Graders usually have conversion tables between different printers although the best graders can grade for the appropriate machine so that if they were grading for the Model C they would think 1 to 50 and if they are grading for the D then 1 to 22 or 1 to 20 for the Debrie. It is only a matter of practice but it is much quicker than grading for one system and then converting.
Cueing Methods
R F Cueing (Radio
Frequency Cueing)
Printer Light Changes
Cueing the film by one of the methods mentioned above is to programme the printing machine to make a change in the printer light settings as defined by the grader. In a century, the number of techniques used to alter the light intensity and the colour of the light to the gate is beyond the scope of this book. To some extent, the different systems are well documented as many were patented and the following takes representative examples of the most commonly used.