P: Full Screen mode: Print & Book modules show wrong colors but output correctly

I am still seeing this issue 10.1.

Just to expand on my post above, the loss of saturation in the zoomed version occurs regardless of whether the image has edits. I can reproduce the effect with an unedited file.

Further I have now realised that I am seeing the same behaviour in the Library module. When zooming in from Loupe view to a higher percentage the image loses saturation.

@bill_3305731  

I guess I didn't introduce myself or post the problem correctly. I print a lot and don't have a problem with lr print module or my monitor or set up or skills. I don't earn money as a photog, but for all intents and purposes I am a professional photographer with superior technical and aesthetic skills. I never, never, never had this problem until I installed Big Sur. Now there may be some compatibility issue others have not incurred. I took an image, made minor adjustments in LR Classic and sent it to the print module as I have done thousands of times. The skin tone went grayish and the colors got flat.

@james_hess_4809339 I appreciate your effort and the time spent on a response. Maybe I didn't articulate the problem. I have an epson printer and a calibrated monitor. I print a lot. Costs a lot. I never, never, never had a problem until I installed Big Sur. Image comes up on monitor in develop. When I go to print module something happens to it. Nothing wrong with monitor.

For the best results, it is also necessary to calibrate round trip with a scanner; a monumental effort. Plus a complete calibration solution costs upwards of $500. I'll give your technique a tryout, I like the price. Thanks. 

The printing experts will tell you that the only way to get accurate prints is to calibrate your monitor with a hardware calibrating device, which I have not done. But I won't argue with that suggestion. The monitor DOES need to be calibrated. I have chosen an alternate method that is not as accurate but has produced satisfactory results for me. I found calibration images on the Internet that I downloaded and printed on my printer without making any adjustments to them whatsoever. Then I use the controls on my monitor and software to adjust the images on screen until they match as closely as possible what the print looks like. Yes, I realize this isn't very scientific, and isn't recommended by anyone who is truly serious about printing. But it has worked consistently for me for several years now.

What I have discovered in my own "problems" is that most often the monitor is set with the brightness too high. Use whatever method you choose, but you must get your monitor to match what the printer is printing. This is probably much more difficult with the Apple retina displays, I'm guessing. If you want to take the time and spend the money for the hardware calibration device and software I understand it's the best way to go.

I wish someone would write a book (PDF preferably) about printing from Lightroom. There are so many gotchas related to printer profiles, printers, printer drivers, the OS and OS updates, paper... I finally gave up and print from the Windows Photos app instead. Experiment has shown that if I boost saturation by about 10 then export at full quality, I get a print that is reasonably close to the screen. At least this week. 

But this is working for one specific printer and paper and likely would need adjustment for any other printer, paper, update to the Photos app, etc. 

The best results, IMHO, is to email the image to an online print shop.

Using Lightroom Classic on Big Sur. Going from Develop to Print, image gets gray and loses some tone, exposure and brightness.

@Rikk

Yes, I'm afraid so. I have just tested it out, and the problem is still present in LrC 10.1... 

Do you still have this issue after updating to 10.1?

I can reproduce something similar using Lightroom 10 and Big Sur. Clicking the "Zoom to Fill" check box in the Print module zooms the image as intended but at the same time the preview is slightly desaturated. On darker images the loss of saturation is barely noticeable but on others it is quite visible.

However, printing the non-zoomed and zoomed versions (to JPEG files) results in identical images (other than the zoom) with no loss of saturation in the zoomed image.