Re: filmscanners: Re: filmscanners: RE: filmscanners: VueScan Problem

["Alan Tyson" <AlanTyson@bknowl.freeserve.co.uk>]

JASC hasn't taken compression/decompression of 48-bit images
seriously because PSP can't work with them. If you do load a
48-bit image you can only save it as 24-bit. For 'serious'
users (which doesn't include me) this is a bad drawback, and
means you're stuck with Photoshop or similar.

I used to use PSP5 as a viewer from within Vuescan, but it's
not necessary any more because (a) Ed put a good viewer in
Vuescan, due to popular demand, and (b) PSP7 loads much more
slowly than PSP5 on my antique (2-yr old) 400MHz Pentium II,
meaning it's an excellent 24-bit editor, but a useless
viewer.

As a *viewer*, Ed Hamrick's *Vueprint* is pretty well
unbeatable, and it's included in the Vuescan licence.

ISTR (seem to recall) that you'll find Photoshop's
compressed tif files may be readable in other programs, but
they're sometimes bigger than the uncompressed ones, so they
load more slowly, anyway.

If you trawl the archives for this list you'll find we last
discussed these issues in February 2001, I think, in the
context of a long argument about jpegs vs tifs.

Maybe those viewers that don't read Ed's compressed 48-bit
files have just lifted a compression/decompression routine
from someone else, without understanding it very well.

Regards,

Alan T


----- Original Message -----
From: Rob Geraghty <harper@wordweb.com>
To: <filmscanners@halftone.co.uk>
Sent: Tuesday, September 04, 2001 11:46 AM
Subject: Re: filmscanners: Re: filmscanners: RE:
filmscanners: VueScan Problem


> Ed wrote:
> > VueScan uses a predictor of 2 - 7 isn't a valid
predictor.  All 2 means is
> > to take the difference between adjacent pixel values
before compressing.
>
> I don't understand.  If a predictor of 2 is invalid why
would you use it?
> The error I get from PSP is "A predictor of 2 is only
supported
> for LZW compression on 8 and 24 bit images".  Obviously
it's a 48bit
> LZW TIFF from Vuescan which causes this error.  An
uncompressed
> TIFF opens fine.
>
> Rob
>
>
>
>