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MMD > Archives > November 1995 > 1995.11.27 > 04Prev  Next


Correcting for Optical "Errors"
By Jody Kravitz

Yesterday, John Grant pointed out that optical systems do not inherently reproduce tracker bar behavior.  I wrote the following reply before I read the other postings from yesterday, and this may be redundant now...

John,
   You are quite correct that in an optical system compensation must be made for the tracker bar & pneumatic behavior and for the expression mechanism's behavior too if you intend to take it to a MIDI format suitable for synthesizers.  Mark Fontana discusses one way of dealing with chain perforations earlier in this digest.  The inverse of is also true -- if you have a "correct" MIDI score, you must massage it to make it suitable for perforating.  One of the arguments for doing reading optically is that you _CAN_ accommodate different roll formats with minimum machining, since you need only re-tool if you need to accommodate a different spool type. Its clear that there is some "retooling" that has to be done in software to "emulate" the correct behavior of the new tracker bar.  I personally like adjusting programs more than adjusting contacts, and you can re-adjust the program later and reprocess the saved image data.  The pneumatic method completely avoids problems with paper-coloration artifacts.  Neither method is perfect.

Jody


(Message sent Tue 28 Nov 1995, 04:22:25 GMT, from time zone GMT-0800.)

Key Words in Subject:  Correcting, Errors, Optical

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