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Re: scanner quality when profiling?

<x-html><!x-stuff-for-pete base="" src="" id="0"><!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<p><tt>You make an interesting point: the scanner's tube deteriorates with
age, like a room fluorescent tube? Would light output decrease precipitously
rather than gradually? Over the last couple of days, I&nbsp; scanned a
series of about 40 Fuji slides on my >2-year-old Nikon LS-20 via Vuescan.
All the slides (Velvia or Sensia) were of comparable density, although
some were taken at dusk or night. At the beginning of the sessions, I was
getting very good results with a gamma of about 2.2 to 2.4 and occasionally
a bit less; these images required very little tweaking in PS to get them
as close to the original as I could hope for (at least as they were displayed
on my monitor).</tt><tt></tt>
<p><tt>Then I noticed I was having to increase gamma to the 3.6-3.8 range
and even >4.0 to avoid very dark raw scans. I double-checked all the Vuescan
and PS settings to be sure that I hadn't changed something. I was still
usually able to correct the raw scans in PS, but the adjustments were sometimes
too drastic and some scanning artifacts began to appear, especially in
shadow areas. I was scanning at 48-bit and making the gross changes in
PS before taking them down to 24-bit so I could use other PS features (the
50+ MB raw files would start eating up too much storage space anyway, so
I throw away the raw scans after converting to 24-bit). When I scanned
some of the same slides on my Agfa Duoscan for comparison, I was able to
use a somewhat lower gamma than on the Nikon (although I doubt that there
is any real correlation between like gamma settings on the two scanners,
since they function quite differently).</tt><tt></tt>
<p><tt>Is it time to replace the tube? Is this something I could do or
will I have to send the unit in for factory service? Maybe it's time to
upgrade my film scanner...</tt><tt></tt>
<p><tt>Steve Jacobson wrote:</tt><tt></tt>
<p><tt>&lt;long snip></tt>
<blockquote TYPE=CITE><tt>When you go to replace the tube, the scanned
image will look somewhat different with the new tube than with the old.&nbsp;
However, scanner profiles should take the tube spectral characteristics
into consideration and compensate for them.</tt></blockquote>
<br><tt>Visit my Web site at <a href="http://ir.clubphoto.com/bernard198799/";>http://ir.clubphoto.com/bernard198799/</a></tt>


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