A project I am working on has all raster/bitmap illustrations in black and orange colours. The orange at full power is
0, 50, 100, 0 CMYK. The artist in some places of the illustration has used lighter opacities of that colour, like
0, 29, 59, 0 and so on.
So, the whole artwork is only using magenta and yellow plates/channels for the colourful bits and black for the outlines.
We want to print this in two colour costing. Previous projects had illustrations in cyan and black colours, which made it very simple cost-wise. Now, I suppose the only option left to make this project 2 colour is to somehow merge the information from magenta and yellow plates into a new spot colour.
The illustrations are in TIFF and they will be placed into InDesign before being exported to PDF.
What are my options? A good workflow for converting channels in Photoshop? Or perhaps some kind of ink mixing in Indesign during export? Or some kind of preflight in Acrobat?
Thank you for any help.