During a roll scan, using an optical encoder, this is the normal screen display.
This is a reasonably good screen image with the bit twiddler pot setting approximately in its mid-range of 10 turns.
Note the quality of the hole image. The "holy grail" of roll scanning strives to acquire a perfect
needle sharp image of the holes, ideally perfectly round a goal recently achieved by Larry Doe. What you see here will produce a good, acceptable quality midi type 1 file.
This a is a marginal screen image with "exposure" set to absolute minimum.
Note the frequent changes in state between the presence of data and the absence of data, within each scan line. Frequent changes of state will dramatically increase file size.
This is a good screen image as a random light bloom flashes across the screen.
Difficult to anticipate, but may be removed by the "speck removal" sub-routine in the software.
Becomes a concern when these light blooms become excessive and fatter than a few scan lines.
In the event of excessive light blooms, best to stop the scan, rewind the roll,
and start over with a reduced exposure setting of the bit-twiddling pot. These random
blooms can be sharply reduced
by making use of a ram drive, rather than directly writing to the hard drive real time.
This is a screen image of a bad random bloom flashing across the screen.
In this case, so big that the speck-removal sub-routine cannot handle it, forcing a rescan.
This is an excellent quality scan as realized by Larry Doe with his MK4 scanner. Note perf images are perfectly round,
and each line of data has well defined changes in state from data (a hole) to no data (no hole).
It has now been determined that there is a direct relationship between these randon light blooms and hard disk activity.
By using a ramdrive, hard disk activity is removed during the scanning process. When completed, a batch file will move the CIS file
from volatile ramdrive to the safety and security of the hard drive, leaving behind an empty ramdrive to receive the next scan.
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