Digital BW, The Print

Thanks Paul.  Robert



On 4/12/02 3:00 PM, "Paul Roark" <paul.roark@...> wrote:

> Robert,
> 
> You wrote:
> 
>> 6 weeks in CA sun through glass takes care of the brighteners.  Now that I
>> have the black light I can check to see if the brighteners are completely
>> gone...or have just partially gone by that point.  The yellowing is not
>> extreme...it just looks like a unbrightened paper.  Nonetheless it is
>> something that will change with time...something I'm trying to avoid.  From
>> what I've seen of your fading numbers my test is about twice the strength
> of
>> your 300 hour test...assuming no major reciprocity failure.
> 
> The typical yellowing pattern I get with EAM is that it is quite fast at
> first and then stabilizes by about 500 hours in my fader.
> 
> Specifically, the yellowing, measuring the change in the difference between
> the blue and red channels when the test strips are scanned (I had no
> densitometer when this test was done) were as follows in a typical test:
> 
> 100 hours in the fader caused 1.5 units of yellowing;
> 
> 200 hours -- 2.2 units of yellowing;
> 
> 300 hours -- 2.6 units of yellowing;
> 
> 400 hours -- 2.7 units of yellowing;
> 
> 500 hours -- 2.8 units of yellowing;
> 
> ...
> 
> 1000 hours -- 2.8 units of yellowing.
> 
> As a practical matter, I have a pretty good idea of how a paper (and/or ink)
> are going to do after 300 hours.  So, that is my standard test time.
> 
> By the way, the Lyson Print Guard spray samples in the fader are at 100
> hours.  Even then I can usually get a fairly good preview of relative
> performance.  If my quick look last night is accurate, the Lyson spray is
> useless for fading and warming purposes (actually less than useless in light
> of the work and lower Dmax).  But, I'll run it to 300 hours to be sure.
> 
> Paul
> http://www.PaulRoark.com
> 
> __________________________________
> 
> 
> On 4/11/02 6:10 PM, "Paul Roark" <paul.roark@...> wrote:
> 
>> Mike noted:
>> 
>>> ... most Fiber Based photographic papers have brighteners are
>>> yellow over time
>> 
>> In my fade testing I've seen no correlation between brighteners and
> fading.
>> 
>> Also, while many seem to think brighteners are a negative to longevity,
> I've
>> seen no hard evidence that they reduce the paper's life.
>> 
>> I'm not sure there is any negative to brighteners aside from the fact that
>> they will eventually "burn out" and cause the paper to yellow a bit.  In
> my
>> tests the typical yellowing is about 3 units of 256, then the papers
>> stabilize and do not further yellow.
>> 
>> Paul
>> http://www.PaulRoark.com
>> 
> 
> 
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----------------------
Robert Morrison
rmorrison@...

310-397-2704

4131 Bledsoe Ave.
Los Angeles, CA 90066