P3D Re: PHOTO-3D digest 2576

[boris@xxxxxxxxxxxx (Boris Starosta)]

Lattie Smart asked:

>
>Date: Thu, 12 Feb 1998 10:24:58 -0500
...
>
>What has been anyones experience w/ hi-res, digital SCANS of original
>slides (and possible touch-ups)  and reimaging them back onto slide film?
>

I just did some experimenting with this.  I was able to secure the use of a
friend's drum scanner, and scanned the slides (two of them, of course) at a
"moderate" 3000x4500 pixels (the scanner is capable of over 8000x12,000 per
35mm frame).  This is a slightly higher resolution than I get from the
service bureau that outputs my computer slides.  Also, I wanted to keep the
file size moderate, and these weighed in at about 40Megs uncompressed.

The results were pretty good.  The electronic "dupe" was still not quite as
sharp as the original (i.e. you could tell them apart), but I doubt that
someone unfamiliar with the original would be able to tell its a dupe.
Certainly, the electronic dupe was significantly better than the optical
dupes I've been getting locally, which I am told are of a very good
quality.  In particular, I was able to suppress the increase in contrast
that is almost unavoidable in optical duping - there was practically no
increase in contrast with the electronic dupe.

Another advantage: no wear and tear on your original, should you want to
make very large numbers of dupes (i.e. no fading).  Also, as mentioned by
Lattie, you can do touch ups.

However, the cost is considerable, even given free use of a $50,000 drum
scanner.  The slides have to be unmounted, the emulsion cleaned and
prepared with an anti-Newton ring "mister", then carefully taped to the
drum.  There was no good way to align the slides, so some rotation
corrections had to be done in software.  To do this efficiently, you need
about 200Megs of RAM.  After the scanning the emulsion needs to be cleaned
again, to remove the anti-Newton mist.  Then each dupe at the service
bureau costs five dollars.  That's ten bucks for a stereo pair.  But it
_will_ be the best looking duped pair you can get.  (Next time I'll scan at
an even higher resolution.  If there is a next time.)

Interesting postscript:  I had the service bureau image the files from
various formats: basically uncompressed and JPEG compressed.  The JPEG
files were about 2.5 Megs, and produced slides that are absolutely
indistinguishable from the uncompressed slides.  I guess that's what JPEG
was invented for.

Compared to the same slide scanned on Photo-CD, the drum scanned file was a
bit sharper (even after downsampling resolution to match the Photo-CD), and
had much better color and contrast (skintones).  I say that for those of
you who use the Photo-CD process.  I'll be sticking to Photo-CD for my Web
scanning, because it is very convenient and quite satisfactory for that
purpose.  But I doubt that electronic dupes imaged from Photo-CD scans
would be better than optical dupes.

Respectfully submitted,




Boris Starosta

usa 804 979 3930

boris@xxxxxxxxxxxx
http://www.starosta.com
http://www.starosta.com/3dshowcase

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