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

["" <steven.chambers@btinternet.com>]

Simon,

I have observed this effect on the Epson Expression 1680 Pro - there is
certainly a small but perceptible jump when switching from the red to the
green channel. On this machine the green channel is also much sharper than
the red or blue - I routinely scan monochrome negatives as positive 16 bit
RGB and convert to greyscale using only the green channel.

Steve Chambers

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Simon Lamb
Sent: 23 May 2002 10:27
To: steven.chambers@btinternet.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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