Do you know why high-volume printing shops want their film processors to have deep developer tanks?
A deep tank has a longer film-path length than a shallow one and thus allows a faster film speed while still ensuring the film has sufficient time in the developer solution. The path length is the distance the film must travel as it is being developed, while the development time is a constant specified by chemical and film manufacturers.
The equation looks like this,
60 sec. x PL/DT = FS
where PL is path length in inches, DT is development time in seconds and FS is film speed in inches per minute.
Let's say you have a shallow-tank processor with a 12-inch path length, and the specified development time is 30 seconds. You can calculate the required film speed to be 24 inches per minute. This means the film processor can develop only one 20-by-24-inch sheet of film per minute.
A deeper processor with a 24-inch path length will process two 20-by-24-inch sheets in a minute, while one with a path length of 36 inches will process three such sheets per minute.
So, if you want to eliminate a production bottleneck at your film processor, you should consider buying a processor with a deeper tank.
John Masarick is newsletter editor for LogEtronics Corp. of Springfield, Va. Phone, (703) 971-1400, ext. 2662; fax, (703) 971-9325.
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