Re: continued solarplate notes

[Jon Lybrook <jon@terabear.com>]

Christina Z. Anderson wrote:
> > So based on your theory Chris, if my ratio is 1:1 screen/image, I 
> > could do 10 seconds/ 10 seconds, or 1min/1min, or 15min/15min and it 
> > wouldn't make a huge difference?  This might be true to some degree 
> > if one is using imagesetter film for both, since the density of 
> > imagesetter film is so heavy.   I'd expect the dots would change size 
> > as time is increased though, since the longer exposures would allow 
> > more light to sneak underneath the edges of the dots.  Easy enough to 
> > test
> > Thanks for the posting!
> > Jon
> Jon,
> Up to a certain point and before a certain point that is my THEORY. 
> I'll really try to blow my theory by a sun exposure of 6/4mn in MT UV 
> rich 5000 ft elevation sun. But you, with it seems maybe the same 
> light source as Ponsaing, are doing 11/10 SECOND exposures compared to 
> 15/15MIN with the same plate??  That's a dif of 7 or 8 stops! Maybe 
> you have another explanation as to why the great variance in 
> times--maybe the aquatint is exposed on UV blocking TMax 100 :)
Very different.  Is he using 5K, 3K, or 1K watts?  Is he using inkjet 
positives on Pictorico or imagesetter film?  If he's using the Dan 
Welden screen and imagesetter positive, the density of both those things 
is so great he could probably do 15 minute exposure times and get away 
with it.  It would have the added benefit of finer dots due to the fact 
that light sneaks under a little during excessive exposures and burns 
out the edges of the dots.   Getting finer dots this way is equivalent 
to a finer dot screen like what I use, but would be alot more abuse on 
the exposure unit.  But heck, whatever works.
> So, given my experience with gum, that there is a range of exposure 
> wherein the dichromate hardens a deeper or less deep layer (with the 
> "bookends" of that range being loss of highlights and midtones and 
> blocking up of shadows and midtones), my wonder is if, in fact, this 
> is true of photopolymer, that there is not one exact best exposure 
> even with the SAME light source and conditions, but a range of user 
> friendly exposure times, given a ratio that is correct--in other 
> words, choose a time and then find the tonally good ratio for that 
> time and then tweak that with a custom curve. This would explain to me 
> the major variance in exposure times I have read everywhere.
I think there is an ideal set of times and conditions, but since people 
have different printers, printer settings, screens, bulbs, etc., etc. 
there's little chance it will be identical from person to person.  I try 
to get the blackest black I can get without creating mushy plates with 
basic screen/image times, then start working with a curve from there, 
tweaking exposure only if absolutely necessary, but once I've found the 
ratio for a particular system, I try never to change it, and instead 
change the curve if, for example, the heads in the printer need replacing.

Jon