[pure-silver] Re: Contrast grades
- From: Luis Miguel Castañeda <octabod@xxxxxxxxx>
- To: "pure-silver@xxxxxxxxxxxxx" <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 27 Jul 2013 08:30:54 +0200
As Claudio said grade numbers doesn't relate between brands but against a
specification which isn't purely visual. You can do what you say with the plus
of being able to sort it visually in gradation using a stouffer strip and a
little patience; procedure isn't complicated and was explained in several
books, iirc ctein one, which is now free to download, was one of them.
On the road
On 26/07/2013, at 20:34, "Claudio Bonavolta" <claudio@xxxxxxxxxxxx> wrote:
> Usually the specs give two numbers:
> - ISO(P) - speed of the paper (no link with film speed ISOs)
> - ISO(R) - contrast of the paper
>
> Example below on page 2:
> http://www.ilfordphoto.com/Webfiles/20135221310281826.pdf
> Said that, the grade numbers usually don't match from a brand to another.
> Even if the ISO(R) number do match, the result may appear different.
>
> Claudio Bonavolta
> www.bonavolta.ch
>
> Le 26 juillet 2013 20:09, Sauerwald Mark a écrit:
>
> I understand how a higher number for the contrast of a paper, or for variable
> contrast papers, using a filter for the higher grade results in a higher
> contrast print. What I am wondering is if there is any objective measure of
> what a contrast grade of 'N' is. If I use contrast grade 3 paper from one
> manufacturer, will I see the same contrast as if I use grade 3 from another
> manufacturer?
>
> I imagine that plotting the exposure vs density you would be able to measure
> the slope of the curve at some point (perhaps when the density is at a
> predefined level,) and the steeper the slope, the greater the contrast - and
> you could define the contrast grades by defining this gradient for each grade
> has that been done? If so, where is it documented?
>
> Mark
>
>
>
>
>
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