Digital BW, The Print

Let me make sure I'm understanding this correctly...

You printed Piezo and MIS VM/VM X3 on different papers for this test?
If that is true, then you cannot draw valid conclusions by comparing 
what I see as apples and oranges... You may say that for a given
paper, these inks fade x amount, but you cannot compare them to each
other. If it was not your intent to compare fading and warming between
the inks, then that was not clear to me...

Thanks,
Cathy



--- In DigitalBlackandWhiteThePrint@y..., "Paul Roark"
<paul.roark@v...> wrote:
> In the latest fade test series, I put test strips of Piezo on Hahnemuhle
> German Etching, MIS VM (nc curve) on EAM, and an experimental
variable-tone
> called VM X3 that prints with the same curves as MIS VM (nc curve).
> 
> I measured fading as a percentage of the starting value and warming
as the
> change in the difference between the RGB red and blue channel
measures.  The
> test strips were scanned into Photoshop with an Epson 1600, and the
> Histogram tool was used to make the measurements.
> 
> 0% (paper white) warming:  EAM (2 samples) 2.4 & 2.3 units;  German
Etching
> 0.6 units.
> 
> 50% patch measures:
> 
> Piezo on German Etching -- Warming = 10.3 units,   Fading = 9.2%
> 
> MIS VM on EAM           -- Warming = 9 units,      Fading = 6.9%
> 
> VM X3 on EAM            -- Warming = 3.1 units,    Fading = 5%
> 
> Note that most of the warming had taken place by the 100 hour mark.  The
> fading was also fastest at first, but it continues much more so than the
> warming.
> 
> The fading of the 90% patch needs to be mentioned.  I measure the
90% patch
> as opposed to the pure 100% patch to see what the shadows will be doing
> because it may indicate whether there is a negative interaction
between the
> black ink and something in the midtone inks (and, of course, the
paper is a
> huge factor that affects all the patches).  A number of people have
noted
> that some components, perhaps including dyes, can actually act as
catalysts
> in fading other components, for example, the black ink.
> 
> (Note that in my fader the light is intense, so the black patches are
> undoubtedly warmer than the lighter patches.  This is probably also
the case
> in the "south window tests" and perhaps all accelerated fade tests.  One
> would expect, therefore, to see more fading in the darker patches.)
> 
> To measure the fading of the 90% patch, I converted the mode to
grayscale
> and used levels to set the white and black points of the control
strips as
> accurately as possible.  The percentage of fading is a percentage of
the 90%
> control strip for each set.  (The MIS VM and X3 are about the same.)
> 
> 90% patch fading:
> 
> Piezo on German Etching -- 55%
> 
> VM X3 on EAM -- 18%.
> 
> Also of note, the Piezo 7000 black on the German Etching paper is
slightly
> darker than the MIS VM black on EAM printed with either the 3000 or
1160.
> When the levels sets the Piezo/German Etching black on 100%, the MIS VM
> blacks read 98%.
> 
> I have sent a Jpeg of the scans to Martin for inclusion in the Message
> Related Files section of the forum.  I did notice, however, that the
Jpeg
> compression slightly affected the measures.  So, measuring those
Jpegs may
> result in slightly different readings than above.
> 
> Paul
> http://www.PaulRoark.com