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

["Anthony Atkielski" <anthony@atkielski.com>]

You should be able to overlay the channels in Photoshop and blend for
differences, and immediately see any misalignment.  If all channels are
aligned, the image will be blank gray; if they are misaligned, the image
will be visible in a kind of pseudo-relief.

----- Original Message -----
From: "Simon Lamb" <simon@sclamb.com>
To: <anthony@atkielski.com>
Sent: Thursday, May 23, 2002 11:27
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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