# Re: cyanotype question

From: Dave Soemarko ^lt;[email protected]>
Date: 09/03/04-01:38:15 PM Z
Message-id: <011001c491ed\$8ed6b950\$0a808080@wds>

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>
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>
> 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>
> > 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
> > > 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
> > > 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 08:28:03 2004

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