Digital BW, The Print

  ----- 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


  Please visit the Group Homepage to check the Files, Bookmarks, Polls and other resources as they are often being updated. The page is at:

  http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

  Please follow these basic guidelines:
  - Include your full name with your message.
  - Include the address of your website, if you have one.
  - As threads develop, trim off excess portions of earlier messages to keep them short.
  - As the topic of a thread changes remember to change the subject header.
  - Good manners are required at all time. No personal attacks or "flames."
  - Complete your Yahoo profile.
  - Before posting a question, search the message archives and the various resources on the homepage. 




  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



[Non-text portions of this message have been removed]

  ----- Original Message ----- 
  From: Paul Roark 
  To: DigitalB&WPrint 
  Sent: Wednesday, October 17, 2001 1:57 PM
  Subject: Re: [Digital BW] Fade test - German Etching & Piezo, MIS VM & X3 on EAM


  Steadman,

  >About that Magical Fading Machine you have there...

  No magic -- just plain and simple.

  >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 fluorescent 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?

  The fader started life as a standard 10" aluminum photo light reflector.  It
  sits facing down toward a white formica counter top.  It is held 1" above
  the formica for ventilation.  At the top of reflector, where the light
  screws in, I've drilled 8  7/16" holes that vent the warm air out the top.
  This pulls the fresh, cool air in the bottom vent.  The paper strips are at
  the bottom lip of the reflector, clipped to the edge of it.  The discreet
  density patches of the test strips  that I measure are placed at the bottom,
  to be as close to the incoming cool air as possible.

  The light used is a florescent light designed to replace normal 100 watt
  incandescent lights.  The light uses about 20 watts but puts out a claimed
  100 watt equivalent.  These lights are now readily available.  I don't know
  the K temp.

  The paper strips are 3 1/2 inches from the light.  I change the paper
  positions during the testing to minimize any differences that may arise from
  uneven light distribution.

  It's impossible to know what the actual paper temperature is, because the
  different densities will absorb different amounts of light and heat up
  differently.  The air temperature as close to the paper surface as I've been
  able to measure is 12-15 degrees warmer than the room temperature.  The room
  temp stays in the low 70's.  I just measured an internal temperature of 82
  degrees F using a standard metal photo thermometer placed as close to the
  paper surface as I could get it's end (which means it was closer to the
  light than the paper, but probably reflected more radiant heat than the
  average paper test strip patch).

  I don't keep track of humidity.  This is southern California, with generally
  moderate to low humidity.

  >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?

  I let "new" test strips at least dry overnight, if possible.  However, I
  have not detected any difference between really fresh and older test strips.
  Of course, the control and test strips must be contemporary.  Here again,
  however, I don't see any significant changes in my dark storage prints, at
  least over the time periods that would typically be involved.

  Actually, the German Etching test strips were sent to me some time ago.  If
  they had already warm-shifted in dark storage, we would probably not see the
  typical light-effect warming.  They acted just like fresh test strips in the
  sense that they warmed in the first 100 hours and then stabilized, for the
  most part, with respect to warming.  This is the same pattern I see in
  almost all combinations of pigments and paper.  (Dyes may not stabilize in
  the same way.)

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

  I scan after the test strips have been in the fader at least 50 hours.
  Between taking them out of the fader and scanning there is usually 15 minute
  or so.  However, I see no evidence of changes after coming out of the fader.
  The dark storage control strips are always, of course, scanned along with
  the test strips.

  That's pretty much the procedure.  I've probably left something out.  So,
  feel free to ask.

  One can debate endlessly the merits of this testing, but for me, it works
  and is better than nothing.  Frankly, the results I see look a lot like the
  graphs MIS put up from RIT.  If all ink and paper sellers would have RIT
  tests run and publish the results, that would be terrific.  It's not going
  to happen, however.  So, where do we turn?  As crude as my tests are, I
  think they are better than the "south window" tests -- faster, more
  consistent and repeatable, and probably less heat.  I really have yet to see
  results that I think are simply inconsistent with what little other
  information is out there.

  Paul
  http://www.PaulRoark.com


        Yahoo! Groups Sponsor 
              ADVERTISEMENT
             
       
       

  Please visit the Group Homepage to check the Files, Bookmarks, Polls and other resources as they are often being updated. The page is at:

  http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

  Please follow these basic guidelines:
  - Include your full name with your message.
  - Include the address of your website, if you have one.
  - As threads develop, trim off excess portions of earlier messages to keep them short.
  - As the topic of a thread changes remember to change the subject header.
  - Good manners are required at all time. No personal attacks or "flames."
  - Complete your Yahoo profile.
  - Before posting a question, search the message archives and the various resources on the homepage. 




  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



[Non-text portions of this message have been removed]