Digital BW, The Print

Joe Davajon wrote:


> 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 which is much stronger lighting.


I'm not familiar with Wilhelm's methods, nor terribly familiar with 
Livick's. But I am familiar with fluorescent lighting. What I know is 
that you can easily get a fluorescent tube that emits totally within the 
  UV; you can get one that is strongly blue; you can get one that does 
near-IR; in fact, if you want to specify a bandpass, you can get a 
fluorescent light to fill it. "Fluorescent light" does not necessarily 
refer to workshop tubes you pick up at Home Depot. And you can certainly 
generate some flux - I worked with a UV fluorescent once that was bright 
enough to give you a sunburn in about 15 minutes if you were working ten 
feet away. Lots of safety requirements had to be met before you could 
work in that lab.

So to me, saying "Wilhelm uses fluorescent lighting, which is lame" 
sounds like it *might* be axe grinding. There isn't enough information 
in the statement to draw any conclusions, but it is obviously intended 
to disparage methodology. The questions you really have to answer is 
*what kind* of fluorescents does he use, what is the aggregate spectral 
curve of the lighting, and what is the incident flux on the fade test media?

I'm unimpressed with discussion of prints which are "exposed to 
daylight," as this is completely meaningless. A print exposed to a 
year's worth of daylight in a sunny room where I currently live (north 
latitude 61.5, in a cloudy climate) is going to last quite a while; a 
print exposed to daylight where I used to live (north latitude 31.5 in a 
clear desert, sun-beating-down-all-the-time kind of place) is going to 
be lucky to look unfaded after a month. Daylight is no standard. If you 
can tie your tests to flux and time, you can at least extrapolate a 
likely lifetime for the print in a given display condition. If you base 
your discussion on "daylight" without specifying the same things I 
indicated in the paragraph above, it means you don't really *know* anything.

--
Jeff Medkeff
Eagle River, Alaska