VMs: RE: RE: Map scans now posted...

["Graham Waddingham" <Graham.Waddingham@xxxxxxxxxxxxxxxxxxxxx>]

Some answers in a nutshell...

Video monitors are relatively low resolution devices. A 17 inch monitor
screen might measure 12.5 inches horizontally. If it is set to 1024x768
screen size, then the image is obviously 1024 dots / 12.5 inches = 82
dpi resolution in that case. A 15 inch monitor at 800x600 might be 75
dpi. A 14 inch monitor at 640x480 might be about 65 dpi.  So you'll
never see a difference between 300dpi and 400dpi, due to limitations of
your screen.

Which raises the question "So when IS there any advantage of using 300
dpi?" The answers to which can be found at
http://www.guides.sk/scantips2/basics1e.html Paper has a higher
resolution than monitors, and so if the final output is printing, then
you should go for higher dpi scans.

Now, as for scanning at intermediate resolutions, many people recommend
scanning at resolutions that are integer fractions of the scanners
maximum. So for a 300 dpi scanner, we should scan only at 300 or 150 or
100 or 75 or 50 dpi instead of "odd" fractional values like 80 or 120
dpi.  What is actually happening is that in a 150 scan, the scanner is
doing a full 300 scan, and throwing away every other bit. In a 175 scan,
the scanner has to 'calculate' the scan by interpolating between the
bits of a 300 scan - and sometimes this can be worse than a 150 scan,
depending on the image.

Hope this helps
Graham

-----Original Message-----
From: GC [mailto:glenclaston@xxxxxxxxx] 
Sent: 19 June 2003 03:22
To: vms-list@xxxxxxxxxxx
Subject: VMs: RE: Map scans now posted...


Nick,

Perhaps someone a little more graphics savvy can explain this
phenomenon, but I've discovered from long experience that the 400 dpi
scan setting has not particular value in graphic presentation and
printing.  For some reason, computers, printers and graphics programs
tend to prefer settings of 75, 150, 300, 600 and 1200 dpi.  There is no
visible advantage to 400 dpi, at least not on Windows systems and in
Paint Shop Pro, but the difference in file size between 300 and 400 dpi
is tremendous.

TIFF uncompressed scans at 600 dpi would be huge, but at this resolution
they would make very good jpeg files.  For most purposes however, 300
dpi is the best size for detailed scans, and with moderate compression
settings will render very well in jpeg format.

Again, somebody with more knowledge in this area may be able to explain
this, since I'm speaking from extensive trial and error experience here,
and not from any definite knowledge base.

GC

> -----Original Message-----
> From: owner-vms-list@xxxxxxxxxxx [mailto:owner-vms-list@xxxxxxxxxxx]On
> Behalf Of Nick Pelling
> Sent: Wednesday, June 18, 2003 7:42 AM
> To: vms-list@xxxxxxxxxxx
> Subject: VMs: Map scans now posted...
>
>
> Hi everyone,
>
> As a temporary measure, I've deleted the test wiki on GC's 
> voynich.info site and have put my first pass TIFF scans of the
map-page there:
> 	http://www.voynich.info/phpwiki/
>
> Can I also put out a big thank you to Anthony, Martin, John, Jim, and 
> Steve, who all generously offered me space on their servers? All much 
> appreciated! :-)
>
> BTW, I plan to rescan the map page at a higher resolution very shortly

> (so that the half-tone artefacting may be digitally removed), which 
> may well yield approx 100MB of temporary scans to post - I may well be
> emailing you
> again soon. :-)
>
> Thanks & best regards, .....Nick Pelling.....
>
>
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