[filmscanners] RE: Re:A scanner question

["LAURIE SOLOMON" <laurie@advancenet.net>]

Preston,
While I am inclined to agree with you on several of your points. But
agreement and disagreement over these points often depends on what the
purpose and use of the scans ultimately are.  For web use as the end use,
clearly, 48-bit 1800 scans are overkill; for printing at the same size or
even an enlarged size by an inkjet printer, film recorder, chromira LED
photographic printer, Lightjet laser Photographic printer, color laser
printer, or even a offset press, it often is overkill if you are sending the
raw scan file directly to the output device ( which you in many case cannot
do without reducing the 48-bit file to a  24-bit file and the dpi to the 300
dpi range).  However, if you are archiving the scans for future unknown
final uses, to scan at the higherst bit depth and optical resolution for
archiving purposes on CDs or DVDs and the like does make some sense in that
it gives you the maximuium information with which to work with at that
future date for the purposes at hand given what might be the then current
requirenments and specs of applications and devices.

You can always down sample or convert 48-bit to 8-bit if necessary so as to
work with an image file in an image editing program when doing adjustments,
corrections, and enhancements; you can always save that modified image file
as a working file which will be sent the particular output device for final
output in accordance with whatever may be its needs.  It is harder and more
problematic to go in the other direction and increase working resolutions
without introducing artifacts and impossible to convert from 24-bit to
48-bit depth so as to be able to add the missing bit depth information.

The only advantage to lower resolution scans and bit depth as you note is
file size; but that may not be of importance to someone who seeks to archive
image files with the highest potential and quality.  Of course, at some
point, storage of all the CDs and/or DVDs needed to archive a single image
file on each may become a significant if not relevant problem, unless you
are a conservatory or library with plenty of shelf space. :-) As for
archiving smaller compressed files using even the high level compression
settings in JPEG or JPEG 2000 so as to be able to keep them on a second hard
drive and not have to worry about longeviety, etc., that might be true but
then you would have to worry about other problems like damaged or corrupted
hard drives, storing archival copies of files in  a single location which
might be open to damage due to viruses, lightning strikes, fires, electrical
spikes, magnetic fields, and the like which would put the longievity of
those files in jeopardy.  Of course, I suppose one could argue that one
could avoid much of this by maintaining a library of hot switchable,
portable, external or internal large hard drives in the 120-200 GB range.
:-)

In light of the fact that HPA wants to print what are probably around 4x6
postcards at an enlarged size of around 13x19 (assuming that HPA has
copyright permissions) an optical scan of 1800 dpi is not that far off in
that it would enable him to resize the image without engaging in any actual
interpolations or resampling so as to produce the size he wants with an
effective resolution of around 600 dpi.  This would give some spare dpi
should he decide that he wants to crop the image and enlarge the cropped
version to 13X19 and still be able to send a file to the printer with a true
resolution of around 300dpi as opposed to an interpolated resolution of 300
dpi which may be the case if he scanned the image in at a lower optical
resolution.



-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Preston Earle
Sent: Sunday, August 31, 2003 12:11 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: Re:A scanner question


"HPA" <tom@historicphotoarchive.com> wrote: "I scan postcards to print
as Super B size 13x19.  The main thing to be sure is that you are
scanning in 48 bit.  This is a big deal.

"I scan at 1800dpi, which is too high, but it is better to err on high.
the scan will fit on a cd, so it is not excessive to my opinion.  I
store one photo per CD, to make filing easier.  While one image is
printing, i can retrieve the CD for the next one, or refile the last
one, without occupying the computer looking up index or storage
locations."
----------------------------

The world can be divided into three groups: (1) People who believe
16-bit data is better than 8-bit data in color photographic scans. (2)
People who know it isn't and try to educate the folks in Group 1. (3)
People who know it isn't and have given up on the folks in Group 1. I
vacillate between Groups 2 and 3.

If you're scanning 4"x6" postcards at 1800dpi, you are getting
7200x10,800pixel scans. Bigger is *not* better. When printed at 13x19
(inch?), prints will be softer than if resized (and sharpened) first to,
say, 3900x5700pixels. Your 16bpc files are probably about 450MB each.
8bpc 3900x5700pixel files would be about 64MB as TIFFs and perhaps 10%
of that as high-quality JPEG or JPEG2000 files. At 7MB per image, you
could keep thousands of images on your hard drive (and archived to your
second hard drive<G>) and not have to worry about CD shuffling,
longevity, or other worrisome CD details. Can you tell the difference in
a 7MB JPEG and a 450MB TIFF printed on your printer?

Preston Earle
PEarle@triad.rr.com

(moving back over to Group 3)


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