Lightroom Classic used on new 16" Macbook Pro with Radeon Pro 5500M

I’ve had my new 16” MacBook Pro now for about a week. It’s equipped with the 2.3 GHz processor, 32 GB ram, AMD Radeon Pro 5500M GPU (4GB) and Intel UHD 630 GPU (1536MB), 2 TB SSD of storage. I would like to know if the behavior I describe below is unique to my MBP using Lightroom Classic or if others have had the same experience.

It’s loaded with Catalina v 10.15.2 and I subscribe to Adobe for Lightroom Classic CC v 9.1, Camera Raw v 12.1 and Photoshop 2020 v 21.0.2.

The first time I attempted to use Lightroom with this new MBP I noticed that it seemed generally all-around slow, especially when using the Adjustment Brush tool. Under Lightroom Preferences > Performance, “Use Graphic Processor” the AUTO was selected. Further investigation revealed that the AMD Radeon Pro 5500M GPU was not in use. This was evident by Activity Monitor's Energy page, right side on the Lightroom Classic line under Graphics Card there was a NO. Also on that Activity Monitor page at the bottom in the Graphics Card box said “Integrated”, meaning the integrated Intel UHD 630 GPU was in use. Also, under About This Mac, Overview & Display, Graphics the Intel UHD Graphics 630 is listed.

Next I opened Photoshop and used the Spot Healing Brush tool without any slowness or hesitation. Looking then at the Activity Monitor, Energy (Lightroom is still open) and to the right side on the Photoshop line under Graphics Card there was a YES. Also on that same Activity Monitor page at the bottom in the Graphics Card box it said High Perf. indicating the AMD Radeon Pro 5500M was now in use. Interestingly thought next to Lightroom Classic it still said NO under Graphics Card.

Going back to Lightroom Classic (Photoshop still open) and attempting the same use of the Adjustment Brush that was sluggish before was now very quick and responsive.

Mac OS System Preference under Energy, "Automatic graphics switching" is defaulted to being checked. This being checked intends for battery energy to be saved by using the integrated GPU when high graphics demand is not needed and to automatically switch to the Radeon Pro GPU when needed. I do not know if being plugged into a power source or being on battery only makes difference in the logic, but I pretty much thus far have only been plugged into a power source with my new MBP.

In any case my issue is: when opening Lightroom before or without Photoshop open, with Automatic graphics switching enabled in System Preference, I will not have the Radeon Pro GPU for Lightroom photo processing.

Work-arounds:

Uncheck Automatic graphics switching in Mac OS System Preference > Energy. This alone will not speed up Lightroom Classic even though under About This Mac, Overview the Radeon Pro and the Intel GPUs will be listed and under Displays the Radeon Pro will be listed. So additionally under Lightroom Preferences > Performance, next to “Use Graphic Processor” AUTO needs to be changed to CUSTOM and the boxes “Use GPU for display” and “Use GPU for image processing” needs to be checked. This will demand the Radeon Pro to be the used GPU.

Note: Strangely with these steps taken Activity Monitor’s Energy page will still show NO for Graphics card next to Lightroom Classic . If by going back to Lightroom Preferences > Performance and to the right side of the page (right top) and clicking “System Info” then click “Close” on the window that comes up, you will then see a YES on the Activity Monitor’s Energy page for Lightroom Classic under Graphics card.To me this is very, very weird...

Seems to me that the auto switching to the high performance GPU, as it is with Photoshop, should also be the same behavior in Lightroom. I have no idea if this is particular to my MBP (something corrupted) or if this is a known issue. I did reach out to Apple support and after latterly two days of going back and forth I was told it's most likely an Adobe issue. I tried to contact Adobe by phone but gave up after waiting a very long time.