Just in case I remove the actions in the future and somebody else requires a similar solution, I’ll very briefly document two different methods of turning a CMYK image to 2 spot colours. In this case, the images were “mostly” red and black/brown in content. This naturally lends itself to using the M and the K channels (M = Spot Red and K = Black), discarding the cyan and yellow. There will not always be a perfect solution to mapping or converting the full range of CMYK colours/tones into 2 colours, so expectations may need to be adjusted. Another method was a little more convoluted, however variations on this approach have been useful in the past and have resulted in similar separations to those created by the old “Powertone” extended dutotone separation plug-in that was discontinued a long while ago… Create a history snapshot to revert back to Convert to Lab colour mode Copy the “a” channel (which holds the opposing magentary-red/green hues) Select the history snapshot to return back to the original CMYK version Create a new channel and paste the clipboard “a” channel data into this alpha channel Apply image the alpha channel to itself, invert on, difference blend mode, preserve transparency, OK Invert the result Apply curves/levels as needed to adjust the tones darker at the shadows or elsewhere Convert to multichannel mode Delete the cyan, magenta and yellow channels Target the black channel and convert to grayscale mode Double click on the alpha channel and change to a spot colour channel and assign a Pantone colour Select the black channel Apply image the black channel to itself in linear burn blend mode 100% opacity, preserve transparency Select the spot red chnnel Apply image the red channel to itself in multiply blend mode 100% opacity, preserve transparency Adjust the tones of each channel with curves/levels where necessary
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