[alt-photo] Re: gum contrast...

[Katharine Thayer]

On May 17, 2010, at 4:00 PM, Paul Viapiano wrote:
>
> Katherine mentions in her website that halving dichromate reduces  
> speed by approx one stop. If you halved the dichromate, and  
> increased the exposure by two, would you effectively get the same  
> print as a 1:1? I'm trying to see relationships in theory here...

Sorry, I missed the second question.  This is a different question  
than the first one, the way I read it, even though your use of the  
term 1:1 makes me wonder if you think you're restating the first  
question.

In the first question, you're not changing the amount of dichromate  
in the mix, so there would be no need to adjust exposure and the  
contrast should be the same in either case.   In the second question,  
you are using half as much dichromate.   If you made two prints, one  
with 2:1 dichromate/gum at 1x exposure and the other with 1:1  
dichromate/gum at 2x exposure (the dichromate solution the same in  
either case) , then you should get a properly exposed print in either  
case, but you wouldn't get the same print, because the reduced  
dichromate would give you  a more contrasty print.