Digital BW, The Print

> 
> I too would like to see how linear the rate of fade is.  

I have a 600 hour read of the K3 ABW and UT7 test strips.  Consistent with
everything we've seen, the rate of fade at the beginning is typically not
the same as later.  I usually assume that the fade rate is higher at first,
but I've occasionally seen apparent increases in density initially, even
when the printing was done over a week prior to the fade test start.  This
might have happened for some of the UT7 samples.  (On the other hand, with
the small size of the UT7 EEM fade, spectrophotometer inconsistencies might
have affected the results.)

All test strips were aged over one week before being put in the fader.  The
4800 test strips were approximately one week older than the UT7 test strips.


Here are some results looking just at the change in Lab L* readings:

4800 ABW on EEM at 50%, 1st 600 hour fade rate:  0.0010 L/Hr.
From 600 hr. to 1944 hr. fade rate: 0.00053 L/Hr.

Here the fade rate was higher at first than later.


UT7 on EEM at 50%, 1st 600 hour fade rate: 0.00005 L/Hr.
From 600 hr. to 1944 hr. fade rate: 0.00015 L/Hr.

Here the best explanation of the results is probably that the UT7 actually
increased in density at the very beginning.


4800 ABW on Premier Art at 50%, 1st 600 hour fade rate: 0.0012 L/Hr.
From 600 hr. to 1944 hr. fade rate:  0.00033 L/hr.

UT7 on Premier Art at 50%, 1st 600 hour fade rate:  0.00032 L/Hr.
From 600 hr. to 1944 hr. fade rate:  0.00019 L/Hr.

Paul
www.PaulRoark.com 






I have no idea
> how
> difficult it would be to record this sort of thing in your next set of
> tests.  I seem to remember reading a Wilhelm article which discussed the
> importance of the length of the stand-down period between printing and
> starting the fade test.  I certainly understand chasing the best possible
> but if the extra fade of Adv B&W K3/K4 is "acceptable" then I would find
> the
> convenience of Adv B&W and colour printing retention to be hugely
> beneficial.  So if the bulk of a 0.7L* fade differential occurred at the
> beginning of the test and subsequent fading differential was trivial then
> I'd be very happy with that.  We also have to remember that a 0.7L* fade
> rate differential on a 50% patch is trivial at best.  You are talking
> about
> density changes of around 0.01 to 0.02 only!
> 
> I also think it would be useful to run a test on the individual K3 vs K4
> inks - ie a colour patch of each ink.  While we do of course print
> greyscale
> which involves blending these inks I'd like a sense of whether or not MIS
> K4
> is better across the board or whether certain inks perform better than
> others.  (This would of course be extremely helpful for the colour guys as
> well.)
> 
> 
> > From: Paul Roark <paul.roark@...>
> > Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Date: Wed, 28 Dec 2005 12:16:22 -0800
> > To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Subject: RE: [Digital BW] On Paul's MIS vs. K3 fade tests . . .
> >
> > Walt,
> >
> >> ... I too am uncomfortable, in principle, with the use of
> >> pure color inks in BW printing (as with the K3s).
> >
> > I'd still like to see some double blind tests to see if people can sense
> the
> > difference visually.  I'm a bit skeptical about that.  So, if there had
> been
> > no significant fading difference, I might well have just gone with the
> > straight k3 approach.  There is no doubt that having color available
> > occasionally is useful even for strictly B&W guys like me.
> >
> >>  What I wanted was a sense of the real
> >> world significance of a L* 0.70 difference in fade given your
> >> light/time exposure.
> >>
> >> This question arises for me partly because such an absolute
> >> difference is very small...
> >
> > Yes, all of absolute fade amounts were small.  The results are only
> > significant if put into the context of the relative fade rates.  There,
> in
> > the extreme case of the ABW mode k3 print v. the MIS UT dedicated B&W
> test
> > strip, there was a 3x difference.  On the other hand, the significance
> of
> > this fade rate difference depends on additional assumptions, such as
> whether
> > the rates we see in initial fading will continue.  So, there are some
> > variables here that are simply not completely known.  For my own
> purposes, I
> > think the results are significant, but I would never go so far as to say
> my
> > tests "prove" that the dedicated B&W inksets are three times as
> lightfast.
> > I've simply seen enough evidence, including but not limited to just this
> > fade test, that I think it's now worth my time to take the next step.
> >
> >
> >> ... I don't know what you estimate your exposure to be
> >> relative to the total display life of a print.
> >> Is the difference you report just the "beginning of the
> >> story,"...
> >
> > Clearly what I'm reporting is just the beginning of the story.  Based on
> my
> > best measure of how bright the light is, I've tried to give some
> equivalence
> > to "Wilhelm years" of display.  However, not only is my equivalence a
> rough
> > estimate, but also I'm not sure how many really trust that the "years"
> > Wilhelm uses are realistic.  (Then again Kodak assumes even less light
> > exposure for its calculations.)
> >
> > Put in the setting of traditional collector's skepticism about inkjet
> > technology, I'm just trying to get the best performance I can relative
> the
> > Epson pigments, which Epson will promote using Wilhelm data.  I'll then
> > simply do the best I can to leverage off those numbers, trying to avoid
> the
> > issue of what the "life" of a print is.
> >
> >
> >> Incidentally, what are you measuring?
> >
> > I use a 50% patch.  I do have some additional test strips in the fader
> with
> > a range of densities.  The 50% patch, however, seems to be
> representative of
> > the midtones, and the black patch is a separate ink.  In the past I've
> > tested the black inks, and the MIS and Epson versions are roughly equal
> and
> > very good -- being basically carbon (not the PKN).  A BO print is about
> as
> > good as it gets in this respect, which is one reason Clayton and some
> others
> > are such fans of that approach.
> >
> >
> > Paul
> > www.PaulRoark.com
> >
> >
> >
> >
> >
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> 
> Please visit the Group Homepage to check the Files, and other resources as
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> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the
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> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from
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> and Moderators. See Group Topic, Rules and Guidelines in the Files
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> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND
> MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
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> MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
> POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
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> OR ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT
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