[Ham-Computers] RE: Scanning A Photographic Slide

[Hsu, Aaron (NBC Universal)]

Slides were designed to be viewed by shining a light *through* them as
opposed to prints which *reflect* light.  Most flatbed scanners are designed
to capture by *reflecting* a light across it's surface.  These types of
scanners often have a "transparency adapter" (TA) option which replaces the
top cover for one that includes a backlight source.  When the TA is
operating, it shines a light *through* the back of the transparency (or
slide) so that the scanner's pick-up assembly can capture the picture.  The
TA is usually an added cost option and most people don't buy one.  Some
scanners sold today include a simple slide or transparency adapter
specifically for slides and negatives, but I don't think the 5100 included
one.

As you mentioned, try it.  At worse, you'll get a "black" scan or a very
dark scan of the slide.  If the scanner was designed to work with
transparencies without an adapter, you might get an acceptable scan.

One thing to keep in mind.  As the slide is only about 1 inch by 1.4 inches,
you'll need to scan it at a very high DPI to get printable results.  But,
only scan as high an *optical* resolution your scanner supports.  If the
scanner is a 600dpi optical device, then scan at 600dpi, not an
"interpolated" 1200 or 2400dpi (interpolated means that the scanner is
adding extra pixels based on several ajacent pixels...in other words,
approximating).  If you don't scan at a high DPI, then the resulting picture
will be aliased (jaggy) due to the enlarging process when printing (1 by 1.4
inch original vs 3 by 5 inch (or larger) printed).  If you scan that 1 by
1.4 inch slide at 300dpi, then a 300dpi print will be exactly 1 by 1.4
inches in size.  To get a 2 by 2.8 inch print, the resolution will drop to
150 dpi.  Up the printed size again to 4 by 5.6 inches and the resolution is
now 75dpi...and, at 75dpi, the print looks pretty, well, ugly.  I think you
get the idea.

High-end slide scanners (like the current Nikon CoolScan series) scan at
4000dpi.  This means you could take that slide and print it at 10 by 14
inches at 400 dpi!  Of course, most of us can't afford a CoolScan.  I
"appropriated" an old Nikon LS-20 slide scanner a few years ago and it does
2700dpi.  Slow as molasses, but it does a decent job.  I'll tell you
something...at 2700dpi, every speck of dust shows up in the scan.  It's a
royal pain to clean the slides and keep them clean as I have a relatively
dusty computer room.  Maybe I should vaccum more often...

One other note...some scanners will not focus properly on a slide if scanned
on the flatbed surface.  The slide holder keeps the film surface off the
scanner glass and causes it to be out of focus.  If the focal ratio of the
scanner is high enough, this won't be a problem.  However, many scanners
have a very short focal ratio and won't focus on anything that's not flat on
the glass (especially the small, light CCD scanners like the Canon LIDE
series).

So, give it a shot!  If your 5100 can get a decent scan and you don't need
to print it, it will be fine for on-screen viewing.  Then try printing it
and see if the results are acceptable.


73,

  - Aaron Hsu, NN6O (ex-KD6DAE)
    {nn6o}@arrl.net
    {athsu}@nbcuni.com
    No-QRO Int'l #1,000,006
    . -..- - .-. .-   ".... . .- ...- -.--"
 

-----Original Message-----
Sent: Tuesday, August 23, 2005 4:17 PM
Subject: [Ham-Computers] Scanning A Photographic Slide
	
Hello All,	
	
I just discovered two photographic slides among the historical radio
documents I recently became the custodian of. I have a HP 5100 flat bed
color scanner with
resolution of 600 or 1200 DPI.	
	
I am being told that I can scan the slide "as is" by placing it on the
scanner bed, as a light will be shone through it etc. I can then save it to
a 3.5 inch
diskette.	
	
I am also being told that I need a special slide adapter to do this.	
	
It would appear the people have done this both ays!	
	
I figure I have nothing to lose, so being as i do not have a special
adapter, why not center the slide, and see what happens?	
	
If any of you have any experience with slides I would appreciate your
suggestions.	
	
Although I can not personally edit with them, I do have several very good
photographic software programs that do handle slides and "slide shows".	
	
Gentlemen, the question is, how to slide?	
	
thank you.	
	
Duane W8DBF	
dfischer at usol.com