>> I'm a little confused about how a duotone stores its information, and whether a profiled inkjet can reasonably proof the file. <<
Hi Mike, Duotone mode is perhaps the most confusing colour mode in Photoshop, due to it's many undocumented features (for composite users). Using this mode for (pre)separated workflows is easy though and is documented fairly well. >> It seems that a duotone is the same file size as a greyscale file, only has one channel yet contains information (visible in the info palette under "Actual Colour") for both plates. How would profile to profile cope with this? << Yes, a Duotone mode file is only a greyscale file, in terms of channels. The colour mapping is generated via transfer curves for one to four plates while the colour is considered to be run at 100% of the selected 'solid' build in use for that ink patch (varied via the original images tones and the t/curves in use). Duotone mode is intended PURELY for separated output, mapping the original tones found in the greyscale file via transfer curves. By all means use duotone mode in composite workflows - just do not expect any accuracy (in numerical terms) from this mode. Duotone mode is intended simply to create a certain required % value of ink in final separated output. That we can get a generally good composite workflow by using this mode for desktop printing or for mode conversions - does not mean that this is accurate or as Adobe intended (they did not). I had a very deep discussion on the ColorSync Users list with Thomas Knoll on this very subject a year or two ago - I learned a lot of stuff about this mode, it is a very complex mode when one starts to worry about the composite view/conversions and anything to do with the composite...but seps are easy and work as one expects. >> And should the end result be an inkjet print, is there any advantage of the duo/tri/quadtone route over converting to RGB and manipulating the channels? << As one gets a visually correct result when going from d/tone mode to RGB - if you are happy with the edits in d/tone mode then yes you can convert to RGB. Or you can just do this in RGB to start with if you prefer using regular methods of colouring a neutral file. For archival, the Duotone mode file is smaller (1 channel) - but one needs to save the colour settings file currently in use for archival with the duotone mode file if one is concerned with composite views (this still may not guarantee that in the future you will get exactly the same composite view, but it helps). D/tone mode is not ICC savvy, you need the CSF to describe how the file in question should look on the monitor or for composite work or conversions in Photoshop. For archival, the RGB file is larger - but one has more choices of file formats and compression to save into and one can embed a ICC profile which does describe the composite colour meaning of the files numbers. If we are talking of proofing a true duo/tri/quadtone using spot inks on a press, without a press proof - then I would not presume that the composite view/conversion/prints reflects the final result in any way, shape or form - although it can at times. It all depends on the settings in use and many other factors. CMYK work is fairly predictable - it is the interaction of spot colour (non CMYK inks - regular, fluro or metallic) and duotone work which is a real crapshoot due to the many variables in the separation, proofing and final printing. There is so much to say on this subject, but it may be better to read the words of Thomas Knoll first hand rather than me going from poor memory...the ColorSync Users list archives should have the thread hidden away somewhere. Stephen Marsh. =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
