P3D Re: Scanned image from Stereo World (Test results)

[michaelk@xxxxxxxxxxxxxxxxxx (Michael Kersenbrock)]

> If we invert the rule-of-thumb that one should scan a continuous
> tone image at twice the screen frequency that used in printing,
> then we should scan the images in Stereo World at 330 to 340 
> spots/inch to retain all the information.

Lee,

Thanks for the measurements!   I wonder if it has been constant
over the years (for Stereo World)?

The 1987-issue Sample scan I made actually was done at 300-dpi and
I downsampled it to the 120 to make the display size "better"
and the file smaller.

I had the scanner-driver set to "auto-contrast" and its
gamma correction factors (etc) set to "off/default".

> I have worked on various document scanning projects and the
> hard question that must be understood in advance is:
>     What is the user going to with the data?
> Obvious there is a cost to scanning at a high resolution
> than necessary.  The danger of scanning at a lower resolution
> is scarificed quality for some applications.  In most cases,

I've downsampled it even further to 96dpi and 75dpi to make
the pictures smaller in netscape, but the text is starting to
take a dive.  I "started" each with the "original" .psd file that
was scanned at 300dpi before downsizing.  That one's REALLY
big if displayed 1:1.  :-)

They are at the same place with names as you would
suspect:

http://www.serve.com/michaelk/sw96dpi.jpg and ..../sw75dpi.jpg

Just in case anybody wants to see the images a bit smaller
to make freeviewing a bit easier.

> the labor of actually doing the scanning dictates that you
> only want to do it once.  Thus it is wise to scan at the
> highest resolution that is practical and down sample later
> if you don't need the information for some purpose (like
> web display).
> 
> There are also issues with representing gray levels.  On my
> Sun monitor, the sample scan didn't have good detail
> in the shadow regions. 

Yes, my Sun monitor tends to make images just generally darker
which tends to muddy the shadows -- even though I usually
have the monitor set to BRIGHT which is how I like it.

Wonder if there is an X-resource for setting a gamma correction
factor.  It's even supposed to be a "3D" board and all.  :-)

Ooops.  That's wrong 3D group stuff.  Disregard that comment...

Mike K.


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