Digital BW, The Print

I suspect the only truth one can say is if you conduct a test of different
ink/paper alongside each other for the same time then under those
conditions, and those conditions only, one or the other will last longer.
So all you can really do is pit them against each other and choose the best
available rather than predicting their life expectancy.


> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 17 Jun 2005 23:00:46 -0700
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Wilhelm vs. Livick?
> 
>> In a post by "yohnnyboy" chhopk@... the writer ...
>> asserts that the Wilhelm data is misleading. ...
>> since Wilhelm's tests are based on fluorescent lighting,
>> they in no way reflect accurately what we can expect for print
>> life for our prints which are exposed to daylight ...
> 
> Sunlight contains a lot of energetic, short-wavelength UV that is filtered
> out by standard window glass.  So, for outside display UV coatings are much
> more important, and prints can be expected to last much less time.
> 
> I think Wilhelm is fairly clear that he tests for indoor display.  For that
> I think his work is fine, although any "years of display" estimate must be
> taken as a very rough estimate that is subject to lots errors due to
> differing display conditions.
> 
> Livick prefers sunlight, but that is only better if you'll be displaying
> your prints in sunlight.  Aside from the UV content of direct sun, it is
> probably the amount of light -- the intensity -- that is most relevant.  So,
> the relative results of testing with either should be close.
> 
> How one defines the "normal" display lighting conditions is an issue Wilhelm
> has pointed to in his criticism of what Kodak is doing.  Kodak seems to
> assume very dim normal display lighting.  I'm not sure what the "correct"
> amount of light is, but when it comes to stating results in terms of "years
> of display" the assumption about display light intensity obviously has a
> direct bearing.  
> 
> Other factors like humidity may also be important.  The brighter and hotter
> the light, the more the print will be artificially dried and the results
> exaggerated.  On the other hand, excess heat might be more like accelerated
> aging than fade testing.  Many companies use the Xenon faders, which are
> very fast and hot.  I think MIS used one of these for its UT testing.  With
> the commercial Xenon light faders there are usually filters that one inserts
> to change from outdoor to indoor lighting conditions.  Sometimes what filter
> was used is not clear when the results are displayed.  However, this might
> make a difference.
> 
> I don't think any procedure is perfect, so I look at all the results and try
> to learn what I can from them.
> 
> For my own uses, I find fluorescent light easier to control in terms of
> consistency and repeatability.  It's cool and efficient, but it also takes a
> long time.  
> 
> I just do comparisons of test strips that are in the fader at the same time,
> and I only look at the relative results.  Assigning a "years of display"
> seems like a stretch.  So, I'll leave that to others (and let them defend
> the results).
> 
> Paul
> www.PaulRoark.com