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

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

Thanks Steve. Seems to be that all scanners have a margin for error set, and
the degree of the misalignment from one scanner to another can vary quite a
bit.

Simon

on 23/5/02 9:47 pm, steven.chambers@btinternet.com at
steven.chambers@btinternet.com wrote:

> 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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