[pure-silver] Re: New color head "discoveries"
- From: "Rob Champagne" <app@xxxxxxxxxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 13 Jan 2005 23:16:18 +0000
And how how are you going to generate a paper curve without projecting
something onto it so that it generates measurable print densities.
robc
At 14/01/2005 00:04 +0100, you wrote:
>Hang on a second!
>Yes, it is true, you can get a true grade 5 from color heads on many papers.
>But, negative development has nothing to do with that. Paper contrast is
>measured as a log exposure range of the paper. This is independent of the
>negative, and consequently, not related to negative development.
>
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>Regards
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>
>Ralph W. Lambrecht
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>On 1/13/05 11:46 PM, "Rob Champagne" <app@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>> I think we agree on this. My point was merely to dispell the myth that it is
>> not possible to get a true G5 with dichroic filtration and that with suitable
>> neg development it is possible. Having done this if you then use an ilford MG
>> filter G5 the resulting print contrast would be G5+
>>
>> robc
>>
>> At 13/01/2005 14:01 -0800, you wrote:
>>
>>> ----- Original Message -----
>>> From: "Rob Champagne" <app@xxxxxxxxxxxxxxxxxxxxxx>
>>> To: <pure-silver@xxxxxxxxxxxxx>
>>> Sent: Thursday, January 13, 2005 9:56 AM
>>> Subject: [pure-silver] Re: New color head "discoveries"
>>>
>>>
>>>> big snip
>>>>
>>>>> The filters of a color head will not give you the full
>>>>> range of contrast available from VC paper with the use of
>>>>> dedicated filters. They should give you a couple contrast
>>>>> grades on either side of "normal" but filters should be
>>>>> used
>>>>> to obtain the maximum and minimum contrast values.
>>>>
>>>> big snip
>>>>
>>>>> ---
>>>>> Richard Knoppow
>>>>
>>>> I wonder whether my observation is true for other dichroic
>>>> filter head enlargers.
>>>> The Ilford Y+M figures for grade 2 on my Durst CLS501 head
>>>> enlarger give approx an ISO grade 1 result on paper.
>>>> It occurs to me that because dichroic filtration does not
>>>> seem to give as much contrast as filter sets, and because
>>>> most new enlargers have dichroic heads, that Ilford, and
>>>> maybe other manufacturers, use this to its advantage in
>>>> terms of film speed.
>>>> To get a true ISO grade 2 using ilfords G2 Y+M figures for
>>>> my enlarger I have to give the negative more development
>>>> which in turn gives allows a faster film speed.
>>>> So what I'm speculating here is that modern film speeds
>>>> may be tailored by the manufacturers to suit printing on
>>>> dichroic heads with Y+M filtration.
>>>> It should be noted that by using increased development of
>>>> the negative the overall contrast obtainable from a
>>>> dichroic is not far short of a true G5 and if you take neg
>>>> development far enough then a true G5 is obtainable from a
>>>> dichroic head.
>>>>
>>>> It all depends on what you are tailoring your development
>>>> to. Do it to 0 filtration and your negs will be too soft
>>>> for G5 on dichroic settings. Do it to G2 Y+M settings of
>>>> your dichroic head and you will get faster film speed and
>>>> availability of higher contrast in your print.
>>>>
>>> What are the other conditions of the comparison? Are the
>>> filters being used in the same enlarger or a different
>>> enlarger? What I am trying to get at is that if the filters
>>> are being used in a condenser enlarger the difference in
>>> contrast will be due to that. Color heads are very diffuse
>>> sources. The type of light makes little or no difference to
>>> the dye images of color but will change the silver image
>>> film about one paper grade.
>>> If the settings of the color head re right for the paper
>>> it should exactly duplicate the contrast of a filter for
>>> that grade. The limitation of the color head is that it may
>>> not be able to reach the extremes of the contrast range of
>>> the paper. This is normally of little consequence.
>>> Since ISO film speed is measured at a fixed contrast
>>> (about right for diffusion printing) a change in contrast
>>> will result in a change of effective speed. changing the
>>> contrast up or down about one paper grade will result in a
>>> change in film speed of around 3/4 stop up or down. Changing
>>> either film conrast or paper contrast should have exactly
>>> the same effect on the print.
>>>
>>> ---
>>> Richard Knoppow
>>> Los Angeles, CA, USA
>>> dickburk@xxxxxxxxxxxxx
>>>
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