RE: Best CI for process

From: Sandy King ^lt;[email protected]>
Date: 10/03/05-04:40:24 PM Z
Message-id: <a06020425bf67603dce54@[192.168.2.2]>

Well, this is not an apples to apples comparison, now is it?
Comparing a step tablet you are holding in your hand with an image on
a monitor is more like apples to meatloaf. The image on the monitor
may seem to show Dmax at Step 7, and that may be where I chose to
place it, but in fact there is visual separation on the step wedges
themselves all the way from about Step 1 or 2 to Step 7. So if am
counting the way you count I would add at least five or six steps to
the exposure scale.

In theory one would like to establish Dmax as the first maximum black
that merges with the next black on the step wedge, but as you well
know, there is really no way to do that with Pt./Pd. because with its
long toe until you get up to about 99% of maximum possible Dmax there
will be both visual and measurable separation between the steps.
Clearly, you have simply chosen to establish your speed point at a
much higher% of Dmax than I do, and that is the reason for different
ES values we have reported.

Sandy

>Well, that wasn't so hard. When I go to the unblinking eye site where you
>show your pt/pd test, I see dmax at step 7 and and dmin and step 18 ,
>showing 12 steps with an ES of 1.8. Step 1,2,3 were all of the same
>density? And paper white is at step 19?
>
>
>If, so that is not where I am counting. Steps 1 and 2 still show separation
>and step 21 is darker paper white in my ES.
>
>
>Eric Neilsen Photography
>4101 Commerce Street
>Suite 9
>Dallas, TX 75226
>http://e.neilsen.home.att.net
>http://ericneilsenphotography.com
>
>> -----Original Message-----
>> From: Sandy King [mailto:sanking@clemson.edu]
>> Sent: Monday, October 03, 2005 4:49 PM
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: RE: Best CI for process
>>
>> Eric,
>>
>> By intelligent I mean the ability to talk apples to apples.
>>
>> We have not been doing that, and based on your description of how you
>> count the steps of a step wedge I now understand why. If I were
>> counting everything but absolute Dmax I too would be reporting am ES
>> of 2.4 or above.
>>
>> Sandy
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> >Sandy, If by intelligent you mean that we all need to agree that there
>> are
>> >not absolute places to start to evaluate a curve, or straight line? There
>> >are not absolute places. There are points of absolute density. ES and CI
>> are
>> >based upon interpretation of useful information that can be arbitrarily
>> >applied.
>> >
>> >
>> >If you are only printing 12 steps on a 21 step scale, one that has
>> densities
>> >range from 0.0 to 3.0, with step 1 and 2 blending and you are only
>> getting
>> >to step 13 before paper white with pure palladium, then our processes are
>> as
>> >different in capabilities as to be creating confusion.
>> >
>> >
>> >
>> >
>> >
>> >Eric Neilsen Photography
>> >4101 Commerce Street
>> >Suite 9
>> >Dallas, TX 75226
>> >http://e.neilsen.home.att.net
>> >http://ericneilsenphotography.com
>> >
>> >
>> >> -----Original Message-----
>> >> From: Sandy King [mailto:sanking@clemson.edu]
>> >> Sent: Monday, October 03, 2005 4:11 PM
>> >> To: alt-photo-process-l@sask.usask.ca
>> >> Subject: RE: Best CI for process
>> >>
>> >> Clay,
>> >>
>> >> I do indeed use a figure of 90% black when plotting with the
>> >> Winplotter program. This gives very close to the same value as when
>> >> measuring a step wedge print in the way I just described to Mark,
>> >> i.e. from the first step about pure paper white to the first shadow
>> >> step that merges visually with the next one.
>> >>
>> >> What I have been trying to figure out from the beginning of this
>> >> thread is is, 1) are Eric and Emille using options which give a much
>> >> longer ES than I am used to in my work, or 2) are we simply using
>> >> terminology and practice that does not allow us to communicate
>> >> intelligently on the subject?
>> >>
>> >> I still have not figured out which is the case, though some of the
>> >> recent communications are making me lean toward the second of the two
>> >> possibilities.
>> >>
>> >> Sandy
> > >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> >Is this exposure scale derived by counting 21-step Stouffer tables
>> >> discernable
>> >> >steps and multiplying by .15? The reason I ask is that I'm betting
>> Sandy
>> >> is
>> >> >using the BTZS plotter program, and the way it calculates exposure
>> scale
>> >> is
>> >> >predicated on picking a maxium black value. I know that Dick Arentz
>> uses
>> >> 90%
>> >> >black for his work....
>> >> >
>> >> >Quoting Eric Neilsen <e.neilsen@worldnet.att.net>:
>> >> >
>> >> >> Sandy, I don't use or test a pure palladium. The smallest amount
>> of
>> >> platinum
>> >> >> that I add is 15% of total metal salt solution. I make my own
>> ferric
>> >> oxalate
>> >> >> and use a palladium solution that is mixed at 5 g NaPd with 3.5g
>> NaCl
>> >> to
>> >> >> make 40 ml. This makes a .7 M solution to match my .7 M ferric
>> >> oxalate. The
>> >> >> Platinum is a .457M solution in potassium version and .7M when I
>> can
>> >> get the
>> >> >> ammonium version. The molarity may be off by +/- .015 as these are
>> >> from
>> >> >> memory but I don't think so.
>> >> >>
>> >> >> My exposure scale for the 1.0ml FO, .15ml K Pt, and .85ml Na Pd,
>> is
>> >> 2.45.
>> >> >>
>> >> >> I make most of my exposures after a 10 minute dry@ 100F and a 30
>> >> minute
>> >> >> humidification @60% RH. I process in Potassium Oxalate at both
>> room
>> >> temp of
>> >> >> 70 and heated to 90F. The exposure test that produced the ES above
>> was
>> >> >> processed at 70F.
>> >> >>
>> >> >> These test were also performed with Starphire glass in the
>> contacting
>> >> >> printing frame.
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >> Eric Neilsen Photography
>> >> >> 4101 Commerce Street, Suite 9
>> >> >> Dallas, TX 75226
>> >> >> 214-827-8301
>> >> >>
>> >> >>
Received on Mon Oct 3 16:40:52 2005

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