"I suspect that there are common components that conflict" Yes that is the case although I haven't seen a conflict it just that they will share the same things including preferences. Does it have to be that way? NO. It is not that way with PS, IL, ID or others. ... View more

I agree as you can Officially do it with all the other Adobe product I think. ... View more

You can't use the 10 catalog in version 9.4 but if your photo edits were saved in the sidecar files then they will be there when you import your photos into a 9.4 catalog. I would suggest you have both 9.4 and 10.1 installed on your system as I have out previously in this thread. That way you can still access the version 10 catalog if you need to. ... View more

@stephane_jean I have detail on another post in this thread how you can update to 10.1 and still keep 9.4. That way you can try 10.1 and if the bug effects you then you can continue to use 9.4. ... View more

You mean care about the stockholders first. ... View more

Projection at its finest. ... View more

Yea and I am running an old 2019 MacPro. ... View more

Here we go with your BS again about antiquated versions of macOS and Mac hardware. That is simply not the case.  ... View more

Yes that should work as long as the edits/manipulations are not saved in the 9.4 library.  ... View more

@louis_brunet Yes it is, but of course you can't use the same library files. And, you can have both open at the same time. One thing to be aware of is that they will share the same preferences, which I have not found to be a problem. Things like the GPU setting will be the same for each. Before install 10.0 make sure you have two copies of the 9.4 folder. Of if 10.0 back to 9.4 make sure you have two copies of the 10.0. You can copy them some where else and the copy them back to the Application folder. Just rename the folder Adobe Lightroom Classic by adding 94 to the end of it and 10 to the 10.x folder. ... View more

It not hardware, more likely some software issue interacting with hardware. But maybe could be font related like the problems with PS 2021. Another thing to try is use a different monitor like I posted earlier where my old MP5.1 went from 10.1 being slow to it being fast and is now still fast with the old monitor attached again. ... View more

Anything is worth a try instead of doing nothing. I no longer have the slowdown problem with 10.1 on two different computers. But if you would rather just complain instead of doing anything about it, so be it. ... View more

*novocastrienne Did you do a clean install of Big Sur? If not might be worth a try on a test partition. Also turn off all fonts once and see what happens. ... View more

This may be old information. Check your GPU History. ... View more

I have experienced the slowdown and also on the same computer with the same monitor after having another monitor on not having a slowdown. And, then putting the old monitor back with the same profile as before and not having the slowdown, recalibrating and new profile with the same software and again not having a slowdown. I am totally baffled by what happened but I am pretty sure it is not the profile. ... View more

I agree with you there. Even though somehow I now have two computers with LR10.1 running without the slowness, but since this is such a mystery I don't trust using it in case the slowness comes back.  ... View more

*Ron_Pfister Did you try zaping the P-Ram. I am still scratching my head as to why my 5.1 had that slow problem and now does not. What could I have done that caused the change? ... View more

*Ron_Pfister Thank for posting this. So now I really have no ideal why LR10.1 is now fast in Library on my old 5.1 box. New 7.1 also is working fine. Hope it stays that way. Just hope Adobe gets this figured out for all you that suffer through this. ... View more

Yesterday I went back and tested LR10.1 on the old 5.1 box with the AOC monitor. No slow down it was fast. Since the old NEC PA127W could no longer hit 5000K or get above 80cd/m it was replaced on the main new 7.1 box. So I connected the old NEC PA127W to the 5.1 box using the same custom profile as before and tested it with LR10.1. I found it to be fast with no slowdowns as before with AOC connected. I decided to sleep on my finding and analyze this for awhile. My thoughts now are that there is some possible caching corruption going on. Possible even font display that is triggered by LR10.1 that isn't by LR9.4. On the 5.1 box the OS is exactly the same as before when LR10.1 was extremely slow. Only thing I did was have another monitor on it for a while. I am thinking that possibly seeing that new monitor changed the caches or ini files that the driver/OS uses for display settings. This would could explain the randomness of this slowdown and why some see changes when going to sRGB or the Low Res setting and why it makes no improvement for others.  Since now I no longer have this problem I can not test this, but for those of you that can here is what I would do.  If you have another monitor hook it up. If LR10.1 is now fast go back to your regular monitor. If you don't have the ability to hook up another monitor, flush all your caches to see if that will make any difference.  ... View more

I just have to wonder why my experience that I posted 3 days ago was different from your experience.  Mac Pro (2019) 3.3 GHz 12-Core Intel Xeon W 192 GB 2933 MHz DDR4 AMD Radeon Pro W5700X 16 GB I have not installed LR10.1 on the stock OS that came with the machine. The new install on new partition plus migration form the old machine/Mojave is working fine though at some point when time permits I do want to do clean install of the apps I use on the clean OS partition. I will do an install of LR10.1 first to test.  ... View more

@mac_nick Did you do a clean install of the OS and then LR10.1? ... View more

From my experience I would guess it is probably the GPU and/or its drivers. I would make a test clean install partition on the machine that has the problems and see if it makes any difference. If not then it is probably the GPU and/or its drivers ... View more

Been configuring the new MacPro which has the W5700X GPU. First off before it arrived I did a clean install of 10.15.7 on the MBP and migrated the production OS 10.14.6 to it. It was my intention to do a clean install of everything which I have a partition started but thought I would go ahead and use the migrated partition if everything was working ok.  Now to the LR10.1 Library Module test on the migrated partition. An AOC monitor with the display profile was hooked up first and the test showed no slowness. Then hooked it up to my two NEC monitors that I normally use and selected the two display profiles from the old MP5.1 that appeared to cause the slowdowns. Still no change LR10.1 was as fast as before. just as fast 9.4. So I went and did a new calibration of both monitors and still no slow down. Not sure what to make of this. Was it a clean install of the OS or the GPU making that much of a difference? Surly others have tried this. By the way the GPU history still shows no activity when in the Library Module, in fact what I found strange was compared with the GPU in the MP5.1 there was absolutely no activity in the GPU History. Make me wonder if there is not some not so kosher attempt at using the GPU for some reason going on when the slowness is showing. ... View more

That is not it. 96GB and I see the same slowness with 10LR. The Library module in LR10 is not using the GPU. ... View more

Hard to believe that LR would really be functional with only 8GB of RAM. I had a MP5.1 with 48GB for a while and was always running in memory limitation. With 96GB it is much better. ... View more

I guess this was the reason. It must have at least 20 characters. ... View more

Not sure why I can't post a screen shot.  MP2012 10.14.6 No I do not have that option. ... View more

@Alexander  Not all of us have that option. Still not sure what combination of hardware and OS gives you that option. All I know is I do not have that option. ... View more

"Now, LR is having performance trouble with some custom-made profiles." But there is something else that triggers this. The same custom-made profiles do not make LR10 behave the same on different systems. ... View more

Same here and I agree. ... View more