Video school about digital negatives for alternative processes. This video is about so-called Base Exposure Time, or Optimum exposure time, or Standard printing time, in short, how we expose photo emulsion (cyanotype, platinotype, salt print, etc.).
For more info about digital negatives for alternative printing go to http://www.easydigitalnegatives.com. More info about books on http://www.photomrhar.com.