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

["Simon Lamb" <simon@sclamb.com>]

Constantine

That's interesting.  I assume you mean +/- 1 pixel between each channel, so
in effect there could be a two pixel gap between red and blue, yes?

Simon

----- Original Message -----
From: "Kapetanakis, Constantine" <KAPETAC@polaroid.com>
To: <simon@sclamb.com>
Sent: Thursday, May 23, 2002 1:19 PM
Subject: [filmscanners] RE: Channel alignment test for B&W scanned as RGB


> 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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