Digital BW, The Print

Steve,

> Interesting that the colour shift is extremely close - really only the
> luminance figures have anything close to a meaningful difference.  Am I
> reading your numbers correctly?

Yes, that is how I see it also.

>  Where you have a positive change in L* is that a fall in L* or increase? 

Where there is fade, the change in L would be positive.  Where the Change in
L is negative, there is an apparent increase in density as opposed to
fading.

I've seen density increases before, and I'm not sure if the carbon actually
increases a bit initially or if the variance is in the meter or control
strip.  The X-Rite is not as stable as I'd like.  As such, the initial
measure and the post-fade-test measure might be affected by the meter
variances.  So, I measure all at one sitting and I also measure both the
control strip and fade test strip.  The control strip, of course, might be
affected by the printer variances, even though printed at the same time on
the same piece of paper.  Some of the negative L changes in this test were
negative both with respect to the initial, pre-fade-test measure and the
control strip.  However, that doesn't really answer the question with 100%
certainty.  At the price of a spectrophotometer I can afford, consistency
from session to session is just not good enough given the very small changes
that we're talking about.  On the other hand, within a single measuring
session, the consistency is sufficient for the relative measures -- the
comparisons -- to be valid.

> I would also suggest that the differences in L* are trivial.

These are just initial readings.  A longer test is needed to be sure what is
going on.  However, in the past, initial readings have been good predictors
of relative performance over a longer test.

That said, I think the fade rates (not absolute amounts) are significantly
different.  They may indicate that UT7 prints are almost twice as lightfast
as the K3 images printed with the AB&W mode.  The pattern was repeated on
all papers tested.

> This should give UT7 purchases a lot of assurance with respect to 
> the relative endurance of their ink.

Yes, but it might make K3 users wonder why they are paying so much more.

I read the results as indicating a rip for K3 or switching to UT inks is
needed for ultimate lightfastness.  The test I did could not isolate where
the relative K3 weakness is coming from -- it could be just the additional
color inks, or it could be the entire inkset.  No UC test I've done has
matched the UT inkset, but the fade rate differential noted here is more
than I've seen in past tests, in particular the test with the UC-based UT7
equivalent I made.  A test with a strip printed with a rip and the minimum
color ink needed to neutralize the warm gray inks will probably be in the
next phase of the test.  This will be able to tell how much of the
differential is coming from the excess of color inks in the ABW mode prints.

Paul
www.PaulRoark.com 






> 
> 
> > From: Paul Roark <paul.roark@...>
> > Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Date: Tue, 16 Aug 2005 16:05:43 -0700
> > To: DigitalB&WPrint <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Subject: [Digital BW] Fade test -- 4800 v. UT7, MIS old v. new, &
> Kirkland
> >
> > My latest fade test (compact fluorescent light) reached 600 hours.  So,
> I
> > have some initial fade results.
> >
> > The short version:  UT7 showed less fading than the 4800 "Advanced B&W"
> mode
> > prints both in the highlights and at 50%; the MIS new base does not
> appear
> > to negatively affect UT performance; and inks on Kirkland paper are very
> > stable.
> >
> >
> > Notes: The results are expressed in Lab and were read with the X-Rite
> DTP 22
> > spectrophotometer.  The same paper batches were used for all
> comparisons.
> > The results shown are the average of 3 readings.  The affects of the
> > variability of the spectrophotometer were minimized by reading
> comparison
> > test strips at the same time.  The actual starting, pre-fade densities
> may
> > vary from the control test strips, but comparisons based on the pre-fade
> > measurements resulted in similar comparisons.  The UT7 comparison test
> > strips were printed with "neutral" curves that were modified to match
> the
> > density and tone of the 4800 test strips as closely as reasonably
> possible.
> >
> >
> > Spectrophotometer readings:
> >
> > EEM 0% (paper white) Control: (96.83, 1.03, -3.49)
> >
> >                      Change: (-0.04, -1.4, 4.48)
> >
> >       Comment: As we know, the paper yellows.
> >                This will affect mostly the highlight results.
> >
> > 4800 EEM AB&W Neutral 5% Control: (92.76, 1.20, -3.79)
> >
> >                          Change: (0.16, -1.49, 4.92)
> >
> > 7600 UT7 Neutral 5% Control: (92.79, 0.83, -3.98)
> >
> >                     Change: (-0.02, -1.59, 4.94)
> >
> >
> >
> > 4800 EEM AB&W Neutral 10% Control: (88.35, 1.07, -3.11)
> >
> >                           Change: (0.52, -1.39, 4.73)
> >
> > 7600 UT7 Neutral 10% Control: (89.18, 0.34, -3.34)
> >
> >                      Change: (-0.04, -1.41, 4.53)
> >
> >
> > 4800 EEM AB&W Neutral 50% Control: (53.55, 0.72, 0.38)
> >
> >                           Change: (0.67, -0.55, 2.04)
> >
> > 7600 UT7 Neutral 50% Control: (54.04, 1.96, -0.27)
> >
> >                      Change: (0.08, -0.68, 1.93)
> >
> > 2200 UT7 New Base 50% Control: (53.53, 1.17, 0.14)
> >
> >                       Change: (-0.14, -0.68, 2.04)
> >
> > Kirkland UT7 50% Control: (56.54, -0.52, -4.17)
> >
> >                  Change: (-0.33, -0.56, 1.24)
> >
> >
> >
> > Paul
> > www.PaulRoark.com
> 
> 
> 
> 
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