Re: filmscanners: VueScan Question

[Arthur Entlich <artistic@ampsc.com>]

Hi Ed,

Again, not to be argumentative, but, I do understand it is the same CCD.

That isn't the issue.  We know that, for instance, typically the blue
scan is noisier than the green or red, right?

I have no idea what type of response the infrared sensitivity of the CCD
is, but I'm (guessing) that the infrared scan looks nothing like the
visible light spectrum scan, and isn't influences at all in the same way
to shadow density of the visible light scan.

Have you tried my suggestion just to see if it makes any visible
difference? (perhaps just doing a compare of the IR scans in Photoshop
might give a clue).

Can you perhaps post an example of what the infrared scan looks like of
a typical image?

If you are stating that the CCD has the same response to IR light as to
visible light, then I am guessing the dICE system is adding a certain
amount of random noise to the scan, in fact, it is, in effect doubling
it in a one scan situation, since each scan introduces a different set
of noise and the they are subtracted from one another.

And again, the question I asked last time begs to be answered:

If the visible light scan introduces erroneous random "noise"
artifacting in the shadow area data, and then the dICE infrared scan
does the same thing, (capturing different noise and random errors)
wouldn't that introduce a second level of errors, since the dICE scan
would have different random pixel data (noise) than that of the visible
light scan, and when the subtraction formula occurs, some data would
either be subtracted that should not have been, or not subtracted that
should have been?

I think it may be time to ask our friend from ASF for some comments
about how CCD's respond to IR, etc.

Art




EdHamrick@aol.com wrote:

   > In a message dated 6/4/2001 10:38:06 PM EST, artistic@ampsc.com writes:
   >
   >
   >> I'm guessing, but I would be surprised that the infrared light
   >>  scan would have very much noise artifacting in it.
   >
   >
   > The exact same CCD and A/D converter is used to scan the
   > image in infrared and visible light.  The only difference between
   > the two scan passes is which lamp is turned on.
   >
   > Regards,
   > Ed Hamrick