Re: cyanotype question

Dave,

Yes, I got that. With each additional *stop* of exposure the tones on
the print should move up by two steps. Starting with 100 units we would
see a shift by two steps on the print at exposures of 100, 200, 400,
800, 1600,...units over the entire scale.

I don't know where I got confused here. I think my previous post is
saying the same thing (up to the point of me saying the low end should
move upward faster which I see is wrong now) only using a different unit
(i.e., 250 vs. 100). I'm testing at an interval of 250 units since that
visually appears to give me maximum density at step 1.

But, looking at the actual test strips, I don't see this smooth shift in
tones on both ends. It appears empirically that the lower steps are
shifting upward faster than the higher Theoretically, that shouldn't
happen based on the numbers we've both been playing with.

Maybe the upper values are just more fragile and are washing away during
processing so it appears the low steps are creeping up at a faster rate.

Thanks for the clarification.

Joe

>>> fotodave@dsoemarko.us 09/03/04 3:38 PM >>>
Well, actually what I wrote below that "step 1 and step 5 should move up
2
steps" doesn't make really make sense, but I think you know what I meant
by
context. What I meant was that both step 1 and step 5 had received
double
exposure, so step 3 and step 7 should the same as step 1 and step 5 of
previous exposure.

Dave S

----- Original Message -----
From: "Dave Soemarko" <fotodave@dsoemarko.us>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, September 03, 2004 3:33 PM
Subject: Re: cyanotype question

> Joe,
>
> The problem is with interpretation of log scale or transmission
density.
> Maybe the following numbers will clarify:
>
> If you expose for 100 units, step 1 receives 100 units, and doubling
this
> exposure means an actual exposure for 200 units.
>
> But when you expose for 100 units, step 5 only receives 25% of the
exposure,
> so it receives only 25 units, doubling the exposure for step 5 means
only
an
> actual exposure for 50 unit.
>
> Now when you expose for 200 units, step 1 receives 200 units, and step
5
> receives 25% of that, which is 50 units; so both step 1 and step 5
should
> move up 2 steps.
>
>
> Dave S
>
> ----- Original Message -----
> From: "Joe Smigiel" <jsmigiel@kvcc.edu>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Friday, September 03, 2004 2:12 PM
> Subject: Re: cyanotype question
>
>
> > Dave,
> >
> > Can you cite the problem with my interpretation? I thought I was
saying
> > the scale would shift upward at both the lower and upper end, just
> > moreso and faster at the lower end.
> >
> > If we look at the steps, their corresponding densities and
transmissions
> > this is what we have (approximately and I've rounded things a bit to
> > simplify...step 1 is actually 0.03 density and <100% transmission,
> > etc.):
> >
> > Step 1, 0.00 density, 100% transmission
> > Step 3, 0.30 density, 50% transmission
> > Step 5, 0.60 density, 25% transmission
> > Step 7, 0.90 density, 12.5% transmission
> > Step 9, 1.20 density, 6.25% transmission
> > Step 11, 1.50 density, 3.1% transmission
> > Step 13, 1.80 density, 1.6% transmission
> >
> > My thought was that if the 250 unit exposure was "correct" to get
some
> > tone, say, max print density at step 1, then another identical
> > arithmetic increase unit exposure (250 units) would be sufficient to
> > produce the same tonal value (i.e., max d) at step 3 effectively
> > shifting the scale upward two steps at that point. However, up
around
> > step 13, that arithmetic unit increase has an insignificant effect
on
> > the resultant tone so that there is no perceived upward sliding of
the
> > tonal scale at that point. Its going up a bit at that end, but not
> > enough to discriminate visually.
> >
> > In the example, to get step 5 to max d would require 250 + 250 + 500
> > =1000 units.
> > Step 7 would need 2000 units (=250+250+500+1000) to achieve the same
> > tone, step 9, 4000 units, and step 11 would require 8,000 units. To
> > match at step 13 would require 16,000 units. As a result, the low
end
> > is shifting much more rapidly than the high end as exposure is
increased
> > (regardless of whether you talk of arithmetic or geometric exposure
> > units).
> >
> > If I'm missing something here, please explain it in a bit more
detail or
> > point me to a good reference so I can understand it better.
> >
> > Thanks,
> >
> > Joe
> >
> >
> > >>> fotodave@dsoemarko.us 09/03/04 12:31 PM >>>
> > Hi Joe,
> >
> > Your interpretation of densitometry or log scale is not correct (no
> > offense
> > intended). If you double the exposure, the scale should shift up on
both
> > lower and upper end. In hand-coated materials, sometimes it is not
> > exactly
> > like that because of many factors including mechanical factor
> > (repeatibility
> > issue) and visual factor (the low and high ends are toe and shoulder
> > region,
> > so when you shift, the change/difference might not be that visible).
> >
> > But looking at your original data, I think the problem is something
> > else.
> > Could it be the warming-up factor of the exposure unit/light? You
could
> > probably try warming the light up for about 5 minutes and repeat
your
> > test
> > and see if there is any difference.
> >
> >
> > Dave S
> >
> > ----- Original Message -----
> > From: "Joe Smigiel" <jsmigiel@kvcc.edu>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Friday, September 03, 2004 12:01 PM
> > Subject: Re: cyanotype question
> >
> >
> > > Hmmm. Actually the effect is beginning to make sense to me based
on
> > > what you've just said. The 2 step gain is on the low end while
the
> > > higher zones are not increasing as much. The lower densities'
> > > transmissions are closer to 100% so an arithmatic unit increase in
> > > exposure would have a relatively greater effect there than on the
high
> > > zones. In other words, if max density is reached on step 1 which
has
> > a
> > > density of approximately 0.00 an additional 250 units would really
> > flood
> > > the adjacent steps with exposure effect. At the same time, step
13
> > > transmits only about 1.5% so it would require a huge arithmetic
> > increase
> > > to make a geometric increase of 2 steps (1 stop density) at that
> > point.
> > > Part of the exposure effect is also probably masked by the printed
out
> > > image in both the low steps and higher ones, but more pronounced
at
> > the
> > > lower end. Add to this a possible intermittency effect as well as
a
> > > dark or drying effect. I don't think I would be able to isolate
the
> > > variables enough to actully solve this dilemma.
> > >
> > > It really makes me see why the density range of the negative
becomes
> > so
> > > important and why the negative density range needs to be tailored
to a
> > > specific process and set of materials. I guess the easiest
conclusion
> > > is that an additional unit of exposure isn't just going to shift
the
> > > scale along the stepwedge evenly (as I assumed earlier) and the
degree
> > > to which this is evident actually depends on where the unit print
> > > exposure matches the overall negative density scale.
> > >
> > > I think I'll give this a rest now and fine tune a couple prints.
I'll
> > > post the images somewhere along with the stepwedges in a few days
if
> > > anyone is interested.
> > >
> > > Joe
> > >
> > > >>> Ender100@aol.com 09/03/04 10:13 AM >>>
> > > Joe,
> > >
> > > That's what is sort of baffling.... two steps is equal to a full
stop,
> > > or
> > > doubling the exposure. So you should go up 2 steps when you
double
> > the
> > > time
> > > from 250 units to 500 units....and that is indeed what happened.
> > > However, you
> > > reported that you got two more steps merging when you went from
500 to
> > > 750
> > > units..... that should have only happened if you doubled the time
from
> > > 500 units to
> > > 1000 units.
> > >
> > > Mark Nelson
> > > www.precisiondigitalnegatives.com
> > > www.markinelsonphoto.com
> > >
> > >
> > >
> > > In a message dated 9/2/04 10:19:17 PM, jsmigiel@kvcc.edu writes:
> > >
> > >
> > > >
> > > > Yes. You have it right as far as the mergers are concerned but
I
> > > don't
> > > > follow you on the question about 2 additional steps merging at
750
> > > units. No
> > > > steps merge at 250. Three steps merge at 500 which indicates
the
> > low
> > > end was
> > > > pushed up the scale 2 steps as an additional 250 units was
given.
> > The
> > > same
> > > > thing happened as the exposure was further increased by 250
units to
> > > 750, i.e.,
> > > > the low end was pushed up the scale another 2 steps. This is
also
> > > showing in
> > > > how many steps solarized initially. The highest solarized steps
> > were
> > > 6, 8,
> > > > and 10 for the 250, 500, and 750 unit exposures, respectively.
The
> > > low steps
> > > > are acting in a consistent manner gaining 2 steps with each
> > additional
> > > 250
> > > > unit exposure. It is the high end that is behaving strangely
> > showing
> > > a
> > > > decrease in the rate that the tones print as exposure is
increased.
> > > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
>
Received on Sun Sep 5 08:27:21 2004