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

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

I assume you make this statement because you have the specs for both
machines.  If so, can you tell us what makes the SS120's pixel registration
spec better than the Imacon.

Thanks.

Simon

----- Original Message -----
From: "Kapetanakis, Constantine" <KAPETAC@polaroid.com>
To: <simon@sclamb.com>
Sent: Thursday, May 23, 2002 1:21 PM
Subject: [filmscanners] RE: Channel alignment test for B&W scanned asRGB


> Apparently the specs of the imagon scanner are not as good as the ss120
for
> pixel registration.
> However, the misregistration is there even on the ss120.
>
> -----Original Message-----
> From: Simon Lamb [mailto:simon@sclamb.com]
> Sent: Thursday, May 23, 2002 7:08 AM
> To: KAPETAC@polaroid.com
> Subject: [filmscanners] Re: Channel alignment test for B&W scanned as RGB
>
>
> Art
>
> If it was a difference in the different focal points of different colours
I
> would have thought it would be apparent in all scans, even colour
> transparency, and I have not seen it in transparency scans thus far.  This
> has been noted consistently in black and white being scanned as RGB,
> although as I said, I cannot reproduce the problem on the SS120.
> Apparently, Imacon stated that the misalignment occurs in all scans,
> whatever stock, but you can only see it on monochromatic stock because it
is
> a tri-colour scanner trying to produce completely neutral tones in RGB.
The
> indications are that it is within what they regard as acceptable limits.
>
> As someone who has worked closely with scanners and the technology, do you
> know if there are normally vendor defined limits for the accuracy of the
> scanning equipment, such as in the case of the alignment of the channels
> where, as you stated, the tri-line sensor is actually recording a
different
> part of the film for each color at any one point in time.
>
> Simon
>
> ----- Original Message -----
> From: "Arthur Entlich" <artistic-1@shaw.ca>
> To: <simon@sclamb.com>
> Sent: Thursday, May 23, 2002 11:44 AM
> Subject: [filmscanners] Re: Channel alignment test for B&W scanned as RGB
>
>
> > Are you sure this isn't a result of the different focal points of
> > different colors?
> >
> > You've probably noted that infrared, for instance, has a fairly large
> > difference in focal point than the visible spectrum (the offset is
> > indicated on most lenses as a red line or dot).  This holds true for the
> > visible spectrum as well, but it is not usually that noticeable until
> > you  look pretty closely.
> >
> > However, it is true that the film could shift, wobble or change
> > dimensionally enough that the difference at scanning times/location
> > could show up as well, since the tri-line sensor is actually recording a
> > different part of the film for each color at any one point in time.
> >
> >
> >  >>>=================================>>>> film
> >             \|/    \|/    \|/
> >          ---RRR----GGG----BBB---
> >         |_______________________|
> >               CCD    SENSOR
> >
> >
> > Art
> >
> > Simon Lamb wrote:
> >
> > > 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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