> I'm not sure we're talking about quite the same thing. This is probably > because > I haven't explained myself properly. I am not trying to set up a "rich > black" > spot colour which I can use for type or for black boxes, or something like > that. I'm trying to increase the visual contrast of slightly "knocked back" > photographs, by increasing the depth of black in the photograph, when > printed.
The point here is that your PDF will be CMYK. If your images are RGB they will have to be converted to CMYK during PDF export, using the profile and rendering intent you have chosen. The profile and the rendering intent are what decides how the RGB black in a photo gets converted to a CMYK black. Adjusting the RGB images in GIMP might not give you the expeced result, if it is the profile and rendering intent that is the problem. This is what color management is about, knowing how the printed result will look. To get it to work you either have to make test prints or make sure you have a fully color calibrated workflow. /Peter
