Digital BW, The Print

Paul, 

I am continually amazed at your patience and persistence in the testing department.  If I had an ink company...you would be Testing Honcho and given the title of Grand Fader...(spoken with a raspy "Darth Vader" voice over the office intercom).  

Now on the more serious side...

About that Magical Fading Machine you have there...would you please describe it, how it is built (is it a homebuilt?), how close the paper is to the light tubes, what number of flourescent watts is involved, what type of bulb, what K temp the bulbs are, what temperature the paper surface is during testing, and what the relative humidity is in the tester on averaged basis?  

Those environmental factors may be of interest...given that the testing equipment is what is driving the "fade." 

Also, how "fresh" are the prints when they go in the tester?  Are they already "cured" and dried or are they still moist and "tender" from just coming out of a printer?  

How long do you let them dry before doing the "before" scanning?

All of those questions are important to me...very important. 

Thanks again (seriously...I really do admire your testiness) and with respect, 

Steadman
  ----- Original Message ----- 
  From: Paul Roark 
  To: DigitalB&WPrint 
  Sent: Tuesday, October 16, 2001 6:26 PM
  Subject: [Digital BW] Fade test - German Etching & Piezo, MIS VM & X3 on EAM


  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


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