Digital BW, The Print

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