When exporting an InDesign job with tagged RGB images (black and white image), InDesign converts one image to Indexed RGB and leaves the other as is (Adobe RGB 1998). When I RIP this job, the Indexed RGB ends up as a 1 channel black and the other (Adobe RGB 1998) image is convertet to 4 channel black?
The "indexed RGB E.png" shows how contrast is lost in the lower images which have been convertet to indexed RGB.
Why does InDesign export the images differently?
[ moved to the InDesign forum ]
the other (Adobe RGB 1998) image is convertet to 4 channel black?
Neutral RGB values will always convert to CMYK as 4-color values unless the destination CMYK profile uses a customized black generation.
the Indexed RGB ends up as a 1 channel black
Check InDesign's Info panel—if the image is outputting as black only, it's Color Space will be listed as Grayscale. If you are trying to get 1-color output open the image's in Photoshop, convert them to Grayscale and save as psds.