Re: Back-exposing on plastic (was: Re: Gum transfer

Yves,

No, it is because I want to understand Katherine's point better.

My last paragraph just helps define parameters so we don't go off and have to
explore unrelated issues.

Mark

In a message dated 5/2/06 5:17:59 PM, gauvreau-yves@sympatico.ca writes:

>
> Mark,
>
>  
>
> is it because you want us to buy your book and you don't want to reveal
> important notion or is it something else but anyway your last paragraph below is
> totally incomhensible.
>
>  
>
> Regards
>
> Yves
>
>  
>
>  
>
>
> ----- Original Message -----
>
> From: Ender100@aol.com
>
> To: alt-photo-process-l@usask.ca
>
> Sent: Tuesday, May 02, 2006 3:50 PM
>
> Subject: Re: Back-exposing on plastic (was: Re: Gum transfer
>
>
>
> Katherine,
>
> I am not sure I understand your statement below.  I understand that gum is a
> short scale process (requires a negative of a shorter exposure scale, like
> in the range of log .9 maybe to log 1.2, give or take a log  or a twig—or from
> your example below, between log 1.5 and log 1.8?
>
> I also understand that no curve on a digital negative is going to change the
> exposure scale of a given mix, and certainly the curve is not going to
> INCREASE the printed gum DMax.
>
> What I am not sure I  understand is if you are saying that for a given mix
> of gum printed with one coat, changing the shape of the curve will NOT allow
> you to  get whatever tones you want between the DMax of this given mix (one
> printing) and paper white?  And further that you can only obtain some of the
> tones ?  Which ones?
>
> Let's assume that a digital negative can have a maximum of 256 possible
> tones of density. (If that is ok with you) and that a radical curve is going will
> reduce the number of tones from 256, so  let's  consider a not so  radical
> curve.  Let's also assume that the negative matches the exposure scale of the
> gum mix before the curve is  added.
>
>
>

Best Wishes,
Mark Nelson
Precision Digital Negatives--The Book
PDNPrint Forum at Yahoo Groups
www.MarkINelsonPhoto.com
Received on 05/02/06-04:27:24 PM Z