Re: Platinum and reciprocity
Judy Seigel (jseigel@panix.com)
Mon, 11 Nov 1996 21:16:14 -0500 (EST)
On Tue, 12 Nov 1996, Terry King wrote:
> When you are dealing with papers where the light sensitive materials sit at the
> surface of the paper and within it, rather than in a layer of gelatine on the
> surface, self masking comes into play. The light sensitive salts at the surface
> of the paper darken first at the surface under the thinnest parts of the neg to
> act as a mask slowing down the action of the light on the salts under the
> surface of the paper so that more time is available for the light to affect the
> salts under the denser parts of the neg.
Self-masking occurs in a printing-out process. As the shadows darken they
cut down on the light getting through to the emulsion. Whether the light
sensitive materials are on the paper or in a layer of gelatine is
ancillary or immaterial.
Judy