(Before you ask, have 25+ years of ICC / color management experience, so we can skip the basics)
I’ve discovered a failure in printing from Lightroom Classic to our Canon PRO-300. Normally, I can process an image with Lightroom, use the Soft Proofing feature to accurately adjust it for output against a supplied ICC profile for a particular paper, and for the most part, the prints are pretty darn great – certainly within my expectations. But recently several times, things will sometimes go sideways without warning, and then the same workflow, with the same images, with exactly the same settings above will suddenly produce lurid results.
Since I have no way of monitoring what’s going on behind the scenes, nor do I know what’s *supposed to happen* with the whole Monitor RGB –> LR Adjustments –> Color Sync ICC profile applied –> Print output CMYK, I don’t know where the failure is occurring – Apple’s Color Sync at the OS level, Adobe Lightroom’s color engine & ICC implementation and/or hand-off to the OS, or both. What I _DO_ know, is that if I open an image in LR, or even the Preview app, and ask the Canon to print it with its own color engine on its own papers, it’s pretty darned close to my fully color profiled monitor. While not perfect, nor as good as when an ICC target profile for a particular paper is working, but pretty good nonetheless. This confirms for me that the printer is still working as expected.
How I discovered that this is an intermittent, creeping problem is that I would be printing a series of photos, and then after some time, start to get these wonky, lurid color prints, and couldn't figure out why. Then I tried printing the same images with the Canon’s default color engine, and get the “pretty darned good” results still, as I described above. Once I rebooted my machine though, and tried printing from LR again with a known, previously fine ICC profile (and I’m guessing LR is handing this off to the printer via Color Sync) and sure enough, I was getting good results with the ICC profile again. I don’t know how, nor do I know why, all I know is that eventually it will break and go sideways again without any warning beyond crappy color output from LR when using an ICC profile. (Again, even when the ICC profile starts producing bad results from LR, I can still choose to have the Canon manage the colors directly, and the results are pretty good still even without a reboot) But, it’s the reboot fixing things that is the hint, but has me stumped.
I think there's a serious bug here, and I've wasted lots of time and money trying to figure out. Please don't just point a finger at Apple, or tell me to file a bug there – I do not have the contacts or clout of Adobe to get Apple to listen. Many thanks in advance for the patience in reviewing this.