[Tig] Film Timer Question

peter_swinson at compuserve.com peter_swinson at compuserve.com
Wed Dec 12 00:20:56 GMT 2012

Jean-Clement asked 

Pete, it was quite limiting to have to have one single value for each scene, 
why a system allowing continuous changes during a scene was never invented?

The printer light valves could only adjust in steps of 0.25logE, while this only represents a 12th of a stop in terms of light level, 
due to the curve of the print stock it represents a somewhat larger change on the print. 
Therefore even a single step within a scene would show as a sudden change in density or hue. 
Probably more significant was that in truth the light valve had to be preset by the movement of 7 rotating solenoids 
and only at the actual scene change did a single solenoid transfer the preset values to the vane slit. 
I seem to remember this limited light valve changes to a minimum change interval of 10 or more frames. 
These solenoid operated light valves were in use, I guess into the early 1990's after which stepper motors were used. 
But I reckon many printers still use the old versions. 
Bell & Howell won a Technical Oscar for its invention. 




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