Digital BW, The Print

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
>