Digital negative transparency

There are numerous internet sites which propose how to produce a digital negative.

Some links:

Robert Hirsch

AlternativePhotography.com

Christina Z. Anderson

Dan Burkholder

MP Photography (especially cyanotype)

Eyes On Photography (especially cyanotype)

and more.

And of course on paper see references in previous post.

A concise handout to get started ( workshop on cyanotype):

négatif-numérique (PDF)