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