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[filmscanners] RE: Channel alignment test for B&W scanned as RGB


  • To: lexa@lexa.ru
  • Subject: [filmscanners] RE: Channel alignment test for B&W scanned as RGB
  • From: "Kapetanakis, Constantine" <KAPETAC@polaroid.com>
  • Date: Thu, 23 May 2002 08:19:15 -0400
  • Unsubscribe: mailto:listserver@halftone.co.uk

This is not a new problem. It is extremely difficult to move in perfect
registration a large mass (such as the ss120 cariage assembly ) at a 4000
dpi accuracy.
You will find that the biggest difference will exist between the Red and the
Blue channel.
The specification for Polaroid scanners is +/- 1 pixel of allowed
misresgistration.

-----Original Message-----
From: Simon Lamb [mailto:simon@sclamb.com]
Sent: Thursday, May 23, 2002 5:27 AM
To: KAPETAC@polaroid.com
Subject: [filmscanners] Channel alignment test for B&W scanned as RGB


There is a debate on-going on the Imacon users list regarding channel
misalignment when scanning black and white stock as RGB.  If anyone has the
time to undertake a smal test could you do the following:

1. Scan a black and white negative as Positive and save at max resolution as
16-bit RGB.
2.  Open the file in Photoshop and view at 100%.  Using the channels
palette, skip between the R, G & B channels (Control 1, 2 & 3) and look to
see if the image moves (sometimes by between 2 and 4 pixels) between each
channel.
3.  If it moves then it shows other scanners have the same problem aligning
channels when scanning monochrome stock using RGB sensors, which in some
cases causes the image to show stretching across the grain.

Useful scanners to try this on would be those competing in the Imacon Photo
arena (Nikon 8000, Sprintscan 120, Multi Pro etc.).

Thanks to anyone who can do this test and post their findings.

Simon

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