Digital BW, The Print

Further to my earlier post I like to quote statements from Mr. Livick:
      "FLUORESCENT LIGHTING IS VERY SLOW, IN FACT FEEBLE AND ARTHRITIC WHEN IT COMES TO 
FADING PIGMENTED INKS. CONSEQUENTLY ANY FADE TESTING ORGANIZATION WHICH IS WORKING USING 
FLUORESCENT LIGHTING AS THEIR MAIN SOURCE OF ILLUMINATION, IS NOT ACTUALLY ACCOUNTING FOR 
THE MAJORITY OF PRINT DISPLAY CONDITIONS. EXTRAPOLATIONS WORKED OUT UNDER FLUORESCENT 
LIGHTING WILL YIELD RATINGS FOR EPSON'S LATEST ULTRACHROME INKS THAT ARE APPROXIMATELY 2/3 
HIGHER THAN NORMAL DAYLIGHT RATINGS. IF YOU MULTIPLY THOSE FLUORESCENT RATINGS BY .33% IT 
WILL REFLECT A MORE ACCURATE RATING FOR DAYLIGHT DISPLAY CONDITIONS WHEN USING ULTRACHROME 
TYPE OF INKS."


I Expected that Wilhelm labs would be testing using high energy fluorescents but my 
surprise they are not.  I made an assumption and I was wrong. Mr Livick is right.

Wilhelm  is using a 'friendly' test protocol originally developed by Kodak where even the 
exposures to cool light fluorescents are glass filtered.  In other words your prints 
better be under glass.

It too often occurs that when industry gets involved in designing test methods under the 
umbrella of other organizations,  the method is designed to make the products of the firm 
or firms that propound and sponsor the standard look good.  What you often get is a low 
common denominator so that everyone's products (the firms' involved in the committee) 
pass. A test method that resulted in longevity predictions of 10 years would not sell many 
printers or paper, would it?

According to other papers from Wilhelm, they use highly discriminating colorimetric 
methods to measure very faint changes in the prints accurately. In this way, although the 
light exposure is mild, the measurements are very discriminatory and by extrapolation they 
come to the numbers predicted for longevity.  It all seems to me a little bit manufacturer 
friendly, and why not, it is the manufacturers that pay for the service not the users.

I am coming to see that Mr. Livick did have some ground for his deprecation of the 
Wilhelm's predictions but I can't agree with either that a lumen is a lumen.  I have yet 
to see the exact specifications for the spectral characteristics of the light source and 
although they must exist they should have been included in the same paper as an appendix 
so the reader can readily verify that the light source is not manufacturer friendly too.

As for us users, what that tells us is that the prints better be on display under UV 
filtering glass or else Wilhelm's 70 years predicted longevity will result in the print 
becoming senile in its teens.

Julio Fernandez

JULIO FERNANDEZ wrote:



> Further to my earlier post I like to quote statements from Mr. Livick:
> IF YOU MULTIPLY THOSE FLUORESCENT RATINGS BY .33% IT 
> WILL REFLECT A MORE ACCURATE RATING FOR DAYLIGHT DISPLAY CONDITIONS WHEN USING ULTRACHROME
> TYPE OF INKS."

Does anyone *really* believe this? This quotation claims you have to 
multiply Wilhelm's figures by 0.0033 to get a realistic number. So a 100 
year Wilhelm-rated print life "really" would mean the print will last 
for four months before significantly fading.

I assume everyone here already has experience with their prints lasting 
that long or longer.


> I Expected that Wilhelm labs would be testing using high energy fluorescents but my 
> surprise they are not.  I made an assumption and I was wrong. Mr Livick is right.

It took me less than two minutes on Google to come up with this:

http://www.wilhelm-research.com/ep9600%20print%20permanence.html

where he speaks of his bulbs having emission at 313nm and 365nm. When 
speaking of optical emissions, this would be high energy indeed.

Granted, X-ray and gamma radiation would be even higher energy 
emissions, but I don't think anyone seriously believes that accelerated 
gamma radiation fade testing is relevant to this subject.

Here's my point: Wilhelm Research at least knows where its emission 
lines are. If you know where the emission line is, you probably know its 
flux as well. A few minutes looking around at Wilhelm Research's IST 
papers shows that their test assumptions and conditions are fairly well 
documented. They've done some experiments, they've published their 
results, and they've opened their findings to debate and criticism 
amongst other people who can do similar experiments and publish findings 
that support or conflict with Wilhelm's.

Livick, on the other hand, has apparently published nothing that has had 
peer review. As far as I can tell, his discussion of longevity does not 
appear to include *a single rigorous measurement* of anything - no 
measurement of flux, nor bandpass, nor even a colorimetric 
quantification of print color over time. He provides a few "lux" values 
using a standard camera meter in integrated light, so these 
"measurements" are very approximate and aren't correlated to passband. 
He doesn't use a photometer, he doesn't use passband filters, and he 
offers no UV flux measurements that I can find. The entire discussion is 
built upon a mathematical house of cards, in which "typical" room 
illumination is basically defined as X, outdoor exposure to direct 
sunlight is defined as Y, etc - from which we can multiply all this by N 
(for the number of months), and correct for Y (some nuance of display 
conditions), and firm conclusions are drawn from these extrapolations of 
assumed, unmeasured truths. All this is explained without formulae, 
without graphs - just text, riddled with misspellings at that. A big 
problem is, since important conditions are unmeasured, any small change 
to the function's inputs makes a BIG difference in the derived print 
lifetime. This doesn't strike me as good methodology. He mentions at 
some point that an Ultrachrome exposed to full outdoor sunlight will 
fade in quite a short time - which it will, but he doesn't explain how 
he controlled for other, non-light sources of fading. Etc. I could go on.

This doesn't mean Livick is wrong. I think he's probably right in 
several criticisms of Wilhelm's methods and in saying that Wilhelms' 
numbers can't be taken as absolutes. But Livick's results fall far short 
of providing the kind of data one would want to have if one really 
wanted to *know* how long their prints were going to last. Although we 
know Livick's methods are very imperfect, we don't know how imperfect 
they are. We have a much better idea how imperfect Wilhelm's methods 
are, and that makes their much more valuable.

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Jeff Medkeff
<medkeff@g...> wrote:
> JULIO FERNANDEZ wrote:

> > Further to my earlier post I like to quote statements from Mr.
Livick:
> > IF YOU MULTIPLY THOSE FLUORESCENT RATINGS BY .33% IT 
> > WILL REFLECT A MORE ACCURATE RATING FOR DAYLIGHT DISPLAY
CONDITIONS WHEN USING ULTRACHROME
> > TYPE OF INKS."
> 
> Does anyone *really* believe this? This quotation claims you have
to 
> multiply Wilhelm's figures by 0.0033 to get a realistic number. 

There is a lack of care here: the original source states

"FLUORESCENT LIGHTING WILL YIELD RATINGS FOR EPSON'S LATEST
ULTRACHROME INKS THAT ARE APPROXIMATELY 2/3 HIGHER THAN NORMAL
DAYLIGHT RATINGS. IF YOU MULTIPLY THOSE FLUORESCENT RATINGS BY .33%"

This includes at least one error (probably two) - it seems likely, in
the context of the other text on the site and general experience, that
either the "2/3" figure is correct and the final multiplication should
be 60% or the final multiplication should be 33% and the earlier
figure should read "3 times higher than normal".  

Which seems more plausible? 

 Fluo 100 years    
 Sun  60  years  (2/3 of 60 being 40, total 100)

or

 Fluo 100 years    
 Sun  33  years  

If the latter, the original text is ambiguous, to say the least. 

On comparing with Wilhelm: I can easily imagine that it would be very
hard to make a procedure, based on quite delicate measurements, that
would match to within a factor of about 2 without taking great care to
do so (same equipment, matching procedure).  I had originally written
Wilhelm instead of "Fluo" above - but that would have been quite
incorrect.  
If a few paper/ink combinations have a consistent lifetime ratio
between the two methods it would be reasonable to conclude that both
sets of results are meaningful  (if they are inconsistent it is not
possible to be sure which is more useful without additional
evidence).

I haven't seen all these posts but as a past member of the ANSI committee on Image Stability I can tell you that these people are under great pressure from industry to design some sort of test that will predict natural age.   Nothing so far is a good as true natural aging.  If you run a test at high temp with bright lights and the product fails you worry but redesign the product.  If it doesn't fail you go with it but still worry.

Dave

  ----- Original Message ----- 
  From: john dean 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Sunday, June 19, 2005 6:09 PM
  Subject: [Digital BW] Re: On Longevity tests


  Livick's website is a joke. You only have to look at the artwork shown there to 
  sense that. If we need to exhibit our work in the backyard in mid day then their 
  tests may have some minor curiosity value, if not they are useless and the so 
  called data is meaningless. To destoy an artwork can be done if you look hard 
  enough to find a way to do that. I could go give myself skin cancer too if I was 
  dumb enough to subject myself to pure uv radiation for days on end, but I 
  hope we have more sense than that.

  John




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