I highly suspect one of the following things:
1) I don't understand what the gamut warning feature is supposed to be telling me and I'm attempting to use it incorrectly (operator error)
2) I'm clueless (entirely possible... the more I learn, the more I realize how clueless I really am)
3) The Gamut Warning feature has a bug.
Now before I start I'm working under the assumption that:
1) A good RA-4 printer (Durst, Chromira) properly profiled can reproduce the sRGB color space and a little bit beyond.
2) A properly profiled inkjet can easily reproduce the sRGB gamut and beyond. This is supported by my own experience of looking at the same test prints produced on a Chromira, a Durst Lamda, and an Epson 2200 (I trust the labs I got the test prints back from did a decent job with their profiles (Pechmans for the Durst and Fotoworks for the Chromira... their output is much better than a lab like WHCC which doesn't in my opinion produce very good profiles).
I wanted to create a very basic test file. I created a 2400x3000 pixel file in the sRGB color space at 8 bits (I actually started out with ProPhoto but after seeing the results I was getting I dumbed it down to sRGB). I then created 14 divisions, each with a gradient in it (the divisions were running vertically on the page). I created two sets of gradients for each color those being X to black (where X is the color) and X to white. The values I used are as follows (numbers are in the format of Red, Green, Blue)
So with two sets of that (one going to black, the other going to white) I had 12 gradient strips. I also created a white to black gradient and finally one strip that was grey (128, 128, 128).
Now here's where I got thrown for a complete and total loop. I selected Canon's Premium Matte Highest for their IPF6100 as my profile and then turned on Gamut Warning. If I'm to believe what the Gamut Warning is telling me, with a file in an sRGB color space being printed to Canon Premium Matte paper with an IPF6100, the printer can not reproduce reds above 79,0,0, greens above 0, 199 0 (there was also a gap in the middle of the green) and blues above 0,0,52. The only color it seemed to do good with was yellow which pretty much went to 255, 255, 0.
Also, if I'm to believe the Gamut Warning feature in Photoshop, for the same paper the Epson 2200 has a wider Gamut than the IPF5000 (compared canned profiles for Ilford Smooth Pearl). Now, the Epson 2200 was a great little inkjet for its day but the Lucia inks are by far superior to the first generation UltraChrome inks. I know that wider gamut does not necessarily translate to a better print but, I did not expect to see that.
So, the results I'm seeing don't reconcile with the results I'm expecting to see which is what brings me here. Set me straight folks! I've attached a screen shot of what it looks like with Gamut Warning turned on so you can get an idea of what I'm seeing.