Re: scanners

[Arlen -dot- P -dot- Walker -at- jci -dot- com]

>* Scanning number crunching I received said an 11 X 17, 24-bit color, 300
>dpi scan would take 2 seconds on a SCSI scanner and a whopping *42*
seconds
>on a USB scanner!

Just to be clear. I said the *data trasmission* would take that long. The
length of the scanning operation is up to the scanner; it moves the light
bar as fast as it can read it. If it takes 30 seconds to scan the image,
then the SCSI scanner will take 30 seconds, but the USB one will still take
42 seconds at least.

>  All of the 10,000+ pages we are planning to scan are
>either text or black and white line art (engineering drawings), and we
will
>be scanning at 300 dpi.  Will the speed limitations of USB vs. SCSI be as
>great for this as they would be for color scanning?  If someone could give
>me a formula for this, I would appreciate it.  I did a search on Google
>hoping it would point me to a site with a formula, but all I found was
info
>for consumer scanners, not professional scanners.  One site recommended
>USB!

Formula:

Size of image = (Height * hdpi) * (Width * wdpi) * colordepth

hdpi is the number of dots per inch scanned along the height of the doc.
wdpi is the number of dots per inch scanned along the width of the doc.
(These two numbers are generally identical, but don't have to be.)
Height and Width are measured in inches.
It's quite possible to use other values for size than inches, just make
sure you have the same units -- don't mix dots per inch with millimeters,
for example.

colordepth is the number of bytes per pixel required. Usually this is 4 for
full-color images. Greyscale is usually 1 byte deep. Line art has a depth
of .125 bytes. Hence line art will result in a smaller image than full
color. Line art will also be more jagged in appearance.

This formula gives the number of bytes needed for the raw image, which is
what most scanners transmit to the computer.

SCSI speed limits vary from 4MB/s with the ancient standard up to over
120MB/s. I used 40MB/s in my original calculation as a good general value;
feel free to substitute whatever values apply in the specific instance.
USB speed limits are currently around 12Mb/s.
The case difference is intentional. SCSI is a parallel transmission,
sending a full byte (or more) at a time. USB is a serial transmission and
sends one bit at a time. Hence 12 Mb/s = 1.5MB/s.

Size is in bytes, so divide it by 1.5 to get the USB transmission time or
divide it by 40 to get the SCSI transmission time.

>* If we use a SCSI to USB adapter, will that overcome the problem of
>needing to exclude the workstation on the SMS network?

Not if your IT manager's decision is completely thought-out, rather than
just a knee-jerk. You'll need a special driver for the USB to SCSI adapter,
you see. And the speed of transmission will be the USB speed, as it's the
slower of the two.

>* My understanding is that having a CD writer on a workstation causes just
>as many (potential) problems with the SMS network as the scanner with a
>SCSI card would.  Approximately 30 of the 150 workstations in this
building
>have CD writers.  In that light, it seems that the SCSI scanner wouldn't
>put them out that much more.

That would be my position as well. A CD writer does not use the same
drivers as a "normal" CD-ROM and requires different support software as
well. So each will violate the "uniform system" mandate from IT.

IT departments should support whatever equipment can be justified by good
business-based reasons. Their function is to support the enterprise in its
attempt to make money. If their decisions end up costing the company extra
dollars, they should have a justification for it. So far the only reason
they've given is that it might possibly maybe cause some nebulous extra
work to have to be done at some unspecific future time. So whoever makes
the fiscal policy at your place needs to balance this vague possibility
against the certainty of it costing $1000 more money for the USB scanner,
or the certainty of it costing more technician time if the machine is off
the network.

Questions:

1) Are the systems backed up regularly? If so, why not put the SCSI machine
on the SMS network and treat it like all the others? Then if the IT
manager's pessimism is rewarded with a conflict, simply go back to the
previous backup image and *then* diagnose the conflict manually and see if
SMS service can be safely resumed after some work. $1000 in savings pays
for a lot of technician time.

2) Can IT (or you) do some research on the SCSI choices to drive the
scanner, looking for people doing the same thing? An ounce of prevention is
worth a pound of cure.

ISTM most "professional" quality scanners are SCSI-based, while most
"consumer" scanners are USB. In my time I've found SCSI scanners to be more
reliable than others, but that could simply be because the other scaners
were built cheaply, and not be directly related to the interface choice.

Not to throw another wrench into things, but you might want to look at
firewire-based scanners as well. Firewire support is part of the new PC
spec, like USB, so that may mollify your IT manager a little. Not sure
about availability of 11x17 scanners in firewire, however; I haven't looked
for any, they might still be a year or so away.

Have fun,
Arlen
Chief Managing Director In Charge, Department of Redundancy Department
DNRC 224

Arlen -dot- P -dot- Walker -at- JCI -dot- Com
----------------------------------------------
In God we trust; all others must provide data.
----------------------------------------------
Opinions expressed are mine and mine alone.
If JCI had an opinion on this, they'd hire someone else to deliver it.


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