From: Sandy King (sanking@clemson.edu)
Date: 02/04/03-10:23:52 PM Z
Richard,
I understand your point, and if you read the end of my message
regarding the characteristics of DOP and POP processes I think you
will see that I am suggesting the same thing based on empirical
observation of results.
However, how do we determine if the result we are observing is due to
self-masking and not to some other inherent characteristic of the
process?
Sandy
>I may be misunderstanding the situation, but I thought self masking was
>relatively easy to test. Simply use a step wedge and overexpose.
>A self masking process will give a series of low contrast
>steps at the "shadow" end of the scale.
>
>I have observed this with salted paper, where during my exposure
>calibration tests, I obtained a print of a 21 step with 12 dark steps,
>with the steps just discernable from each other and above these
>the well seperated steps in the "straight line" part of the curve.
>
>If the process gives well seperated steps with a distinct Dmax
>then it is not self masking.
>
>
>Richard
>---
>Richard Urmonas
>rurmonas@senet.com.au
>
>>>As for "self masking" -- from what you say it's impossible to test that so
>>>we can say anything we please. Well, I shall say that there is no self
>>>masking and how will you prove that there is?
>>
>> I actually tried to figure a way to do this with carbon some weeks
>>ago because Dick Sullivan offered the opinion, perhaps on another
>>list, that the print-out image that results from conversion of
>>dichromate to chromate, even in the absence of pigment, should lead
>>to some self-masking in carbon. I don't believe that is correct
>>because of the almost linear response of a carbon curve that you
>>see, in practice. However, to this point I have not been able to
>>figure out a good test for self-masking in carbon.
>>
>>> After all, you can't simply
>>>compare it to another process, because every process has a different
>>>contrast range. And also and therefore the range of every process
>>>(including and especially every paper combo with a particular procedure
>>>and chemistry) has to be tested separately. So what is the meaning in
>>>this context of any *theory* at all? Suppose, if we must have theory, that
>>>I have a theory that cyanotype makes you more beautiful than otherwise.
>>>There are all kinds of reasons for that but it's now 4:21 AM & my bedtime.
>>
>>
>>Yes, it is true that every process has a certain contrast range,
>>although this can usually be modified significantly. However, from
>>a practical perspective we know that certain things are true of DOP
>>processes as opposed to POP processes. With a DOP process you will
>>loose either the highlights or the shadows, depending on amount of
>>exposure, unless the contrast of the negative is carefully matched
>>to the exposure scale of the paper. Assume, for example, that you
>>try to print with a negative that has a higher density range than
>>the ES of the paper. If you print for good shadow detail the
>>highlights will have no texture, whereas if you print for good
>>highlight details the shadows will block up completely and go
>>completely black. And of course I mean a straight print, with no
>>dodging, burning. With a POP process you can print the entire tonal
>>scale of the negative, even when the density range of the negative
>>is much longer than the exposure scale of the process, *but* by the
>>time you managed to get good detail in the highlights you will
>>start to lose contrast in the shadows because of self-masking, and
>>the overall contrast of the print will be significantly reduced.
>>The result of this is that the print will loose overall contrast
>>but the shadows will never go completely dark.
>>
>>
>>
>>Sandy King
>>
>>
>>
>>
>>--
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