[filmscanners] RE: [filmscanners_Digest] hi bit

["Austin Franklin" <austin@darkroom.com>]

Hi Tom,

> Hello afx, I think the slowness is primarily due to the glacial speed that
> the scanner transfers data to the computer.

Unless you have a really old scanner that uses a parallel or serial port,
I'd doubt that the issue is data transfer from the scanner to the computer.
Typically, it is the exposure time that is far longer than the data transfer
time.  A bulb that is weak, or simply bad exposure, can really reek havoc on
exposure time.

If you do the simple calculations for, say, a 35mm negative, 16 bits/color
at 4kSPI, that gives you 4000 x 6000 x 2 bytes/color x 3 colors bytes to
transfer = 144,000,000 bytes.  Data is transferred while the scanner is
scanning...and any processing is done line by line, as it is sent to the
computer.  So, Asynchronous SCSI I goes at, let's say, 1.5M
bytes/second...so that would take 96 seconds...or one and a half minutes.

Say you have 25ms per line scan time, and a 5ns per line overhead, or 30ms
per line.  There are 6000 lines, so just the scan takes 3 minutes.

I'd suggest checking your exposure time if you are getting long scans.
There also could be something wrong with your cable/termination/controller.

Regards,

Austin

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