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[filmscanners] Re: IT8 calibration for slides
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<div align="left"><font face="Arial"><span style="font-size:10pt">I
wrote:</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt"> </span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > I mainly
shoot slides and scan with a Minolta Elite.  Whenever I
scan,</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > irrespective
of whether I use the scanner software or Vuescan, the</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > scans are
too dark and need considerable adjustment to get closer to</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > how they
look on the light box.  (This isn't a monitor issue -
images</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > from</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > other sources
all look fine - and the histograms of the scans back up the</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> > way they
look on the screen.)</span></font></div>
<div align="left"><br/></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Tony
asked:</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt"> </span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> 1.Are you scanning
to produce 16bit/channel files from VS, or 8bit?</span></font></div>
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<div align="left"><font face="Arial"><span style="font-size:10pt">I normally
produce 16bit/channel files
- simply because they always need some degree
of post-processing in PS. </span></font></div>
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<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> 2.What happens
if you use VS 'exposure' controls  (color tab, 
brightness</span></font></div>
<div align="left"><font face="Arial" color="#000000"><span
style="font-size:10pt">> control) ?</span></font></div>
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<div align="left"><font face="Arial"><span style="font-size:10pt">I normally
have to crank the brightness
setting up to anything between 1.4 to 1.7 to get
an image that doesn't look underexposed.  But doing this still leaves a
large gap
between the bottom of the histogram and the black point.  Obviously,
adjusting the
black point in PS darkens the image again so I have to over-adjust the
brightness to
anticipate for this!</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">This happens
both scanning direct
from Vuescan and using a 16 bit linear (raw) file
generated from the Minolta software.  In fact, scans made from Vuescan
sometimes
look slightly darker - but just because the Minolta software sometimes clips the
hightlights when the AE setting is switched off and so returns a marginally
brighter
looking scan.  </span></font></div>
<div align="left"><br/></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> > I
understand that IT8 calibration
is mainly to characterise the scanner's</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> >
response to the film's coloured
dye (thank you Tony for explaining this</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> > so
clearly) but I wonder
if it would help also getting a better balance</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> >
across the shadows and midtones.</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">>
</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> It
shouldn't make much difference
at all unless your particular scanner is</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> for some
reason very divergent
from other Elites. I wouldn't go there, at</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">> least
not yet.</span></font></div>
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</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Well, I have
tried several Elites
over the years and, in this respect at least, they have all
been pretty similar.  I'm not sure if Ed Hamrick did a specific Q60
calibration for the
Elite.  If I remember correctly, when the Elite was introduced, he quickly
worked out that
the hardware was very similar to the Scan Speed and used the same basic
calibration.
However, I doubt if that is the whole issue - if I set VS to use the canned
Minolta profile
rather than the one built in to VS, it does shifts the colour balance and
lighten the image
slightly but not enough to stop the image still looking dark.
</span></font></div>
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<div align="left"><font face="Arial"><span style="font-size:10pt">I know the
scanner output should be
linear but it almost makes me think that Minolta
have deliberately biased the output of the scanner away from the shadows which
is, of
course, where any scanner shorcomings will generally be the most
obvious.</span></font></div>
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<div align="left"><font face="Arial"><span style="font-size:10pt">Thanks for
your input on this Tony. 
It isn't going to break the bank to get one of the
cheap it8 targets from </span></font><font face="Arial"><span
style="font-size:10pt">www.coloraid.de
but it would still be annoying if I got one and find
that it makes no difference!</span></font></div>
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<div align="left"><font face="Arial"><span
style="font-size:10pt">Cheers,</span></font></div>
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<div align="left"><font face="Arial"><span style="font-size:10pt">Al
Bond</span></font></div>
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