We have been running Mojave on our MACs since its 10.14.6 release and it has been running very smoothly. Colour and B&W prints have been accurate and stable. However, since new features in LightRoom and PhotoShop were released which are not supported by or available in Mojave, we felt it was time to explore an "upgrade" to Big Sur. So, out of an abundance of caution, we "upgraded" only one of our MACs to Big Sur. This immediately broke the PhotoShop and LightRoom Classic print pipeline from that MAC. When we printed from it the result looked like prints made without the use of any ICC profile at all. However, prints from Print Tool and ImageNest were perfect. So, this seemed to be an issue between Adobe and Apple. At the same time I read accounts from others who had run into ColorSync related issues after moving to Big Sur. Apparently ICC profiles were hidden i.e. unavailable etc. We never had that issue. Our profiles were listed but were being ignored by PhotoShop and LightRoom - but not other apps.
After a couple of weeks of this and printing only from Print Tool or ImageNest from that MAC, we decided to move it to Monterey because I had read that it had solved some of the ColorSync related issues encountered by others. After doing so we printed our standard image test file from PhotoShop. That test file has been used by us for several years. So we know it well. It consists of a collection of various colour and B&W images and scales. The print from Photoshop immediately appeared as though our profiles were being picked up again. But, two images (one in particular) were inaccurate which begged closer inspection. One of the images in the test file is a pic of a woman with deeply tanned skin tone. The skin was clearly more brown/red - cooler than the correct print or the screen display. Also, after closer inspection we saw that the greens in another image were cooler. In fact the entire file appeared ever so slightly cooler. This was highly unusual.
So, we printed the file from Print Tool and ImageNest again. This time, the print from Print Tool matched the result from PhotoShop i.e. cooler with browner red skin tone in that one image in the file, cooler greens and ever so slightly cooler overall. The print from ImageNest however was a complete failure. It was not picking up the ICC profiles or was not reading them correctly. The result was a crazy, oversaturated, magenta laden mess. So, first, ImageNest is apparently not yet supported in Monterey. More importantly to us, though, was this new colour discrepancy in our standard test file that was apparently created by Monterey. So next we printed the same test file twice to the same printer on the same paper - once from a Monterey MAC and next from a Mojave Mac. The same settings were used for both prints. The print from the Monterey MAC showed the cooler midtone to deep red and the print from the Mojave Mac was normal i.e. that skin tone was warmer and the greens in the other image were less cool.
Further to this, we ran 2 more test prints from a file which is comprised of a 60 patch colour scale and 51 patch grey scale. We run these tests regularly to gain numerical comparisons of profiles and printers in addition to visual comparisons using the aforementioned image based test file. The scales were printed first from the Mojave Mac and second from the Monterey Mac on the same printer and paper with the same settings. After drying, we measured the patches with an i1Pro2 and compared the readings in Patch Tool by Babelcolour. Normally, the results would be almost perfectly matched - certainly well below d/e: 1.0. BUT, the readings from these prints differed significantly. While over half of them read well under d/e: 1.0, half of them, including some midtones of the greyscale and deep reds and greens neared d/e: 1.0 and several were over to d/e: 1.3. This confirmed what we were seeing between the 2 image based test prints.
Something has changed in Monterey. Something is apparently wrong in Monterey. A quick, cursory glance at the Monterey print versus Mojave print might lead one to believe they may be the same. But, fortunately the particular depth of red in that one image of the woman with tanned skin tone has revealed the inaccuracy between the Monterey and Mojave prints quite clearly. It caused us to inspect more closely and we noticed the greens were off as well. I posted our findings on this in another forum. One or two replies were from folks who had printed from PhotoShop or LightRoom in Mojave and Monterey and claimed that their results were identical. As I said earlier, we have used this particular test image set for many years and know it very well. But, if we had deleted the pic of the woman with deeply tanned skin tone from that image set, we may well have missed this inaccuracy. So the degree to which the difference is evident is dependant upon the colours in the tested image. I am very curious if anyone else has seen such difference between prints from these two MAC operating systems.
Mick