Andrew, your story about the red is most interesting because it is precisely intense reds that have been giving me the biggest headache in ProPhoto (hugely over-saturated to the extent the printer couldn't deal with them), but rescanning the negatives in ARGB98 went a long way to taming the red to something believable the printer (Epson 4000) could handle much more successfully - so the reverse of the solution you found.The workflow I use is to keep the image in ProPhoto.
Then, setup your softproof settings for your printer and turn on Gamut warning.
Next, create a hue/saturation adjustment layer for the image.
Start by selecting a colour channel associated with your main problem colour. You can adjust the sliders on the spectrum at the bottom to change the boundaries of the channel.
Then, adjust the saturation/lightness of the channel to bring the problem area under control. You might also find a slight shift in hue might work.
By doing this with each of the problem channels, you can tame your colours into the gamut of your printer.
Of course I won’t say: “As if I haven’t said”. Hope the sense does not get lost due to translation. & Peace!
Just for background info, I recently took the opportunity to bring this issue to Bruce Fraser’s attention:http://forums.robgalbraith.com/showfla....t358022
Now thinking about possible solutions, it’s easily obvious that a best practice for controlled de-saturation is required to move such an excess of out-of-gamut colors from ProPhotoRGB towards the printer space; more precisely into the expectance-sphere of the Lut. In addition to Andrew_Larkin’s post, some further techniques are as follows:
1.) Just convert to a slightly smaller space such as Bruce Lindbloom’s Beta-RGB prior print.
2.) Reduce the contrast on both channels a & b in Lab mode (keep an eye on possible hue shifts).
3.) A Hue&Sat-layer set to Saturation blend mode, combined with either a Color Range selection, or preferably with a selection of out-of-gamut colors. Alternatively, instead of the Hue&Sat.-saturation slider the Channel Mixer can be used.
4.) Assignment of a ProPhotoRGB Chroma Variant as introduced recently:http://forums.robgalbraith.com/showfla....#358826
… and combinations thereof. In any case, SoftProof to the printer profile will contribute for prediction.
Hope this is of help!
P.S.: Sometimes theory is not so bad, too...