[pure-silver] Re: New color head "discoveries"
- From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
- To: PureSilverNew <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 14 Jan 2005 00:04:35 +0100
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.
Regards
Ralph W. Lambrecht
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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