Lightroom Classic slow and stuttering on new, top-spec iMac
I am a wedding photographer using Lightroom 10.2 on a 2021 iMac with everything upgraded to the max, but have performance problems that are driving me crazy!
Lightroom Classic slows down and performance starts stuttering in Develop Module, especially when using local adjustments. The 'brush' is the biggest culprit, but spot-heal can also be super slow - like 10 seconds to render the change.
The symptoms of the problem are that everything is fine for 5-10 minutes after launch, then soon enough the brush tool starts to glitch. Even when not brushing, moving the brush cursor around in a circle is not smooth. It stops for a fraction of a second and then continues. Once you start brushing, this stuttering makes things unusable.
I have GPU turned on (upgraded to the most powerful GPU when ordering the iMac). If I turn it off, then the cursor does not glitch, but then the effect of the brush is so slow that it takes a couple of seconds to catch up. So as long as I work veerrrrryyyy slowly I can limp on. Problem is that as a wedding photographer I have up to 1000 pictures to edit, so this slowness is not workable.
I have a MacBook Pro also (2018) which has no such problems. Ironically I upgraded the iMac to help with performance of LR, PS and Final Cut.
Looking at ActivityMonitor shows nothing unusual in CPU or GPU usage when the problem occurs.
I am a professional photographer and educator, with workshops on LR, PS etc and also before photography was a software architect. I mention these things to give confidence that I have tried everything obvious I can think of to resolve these issues before coming here.
My catalog is on my internal SSD, and images are on an external HDD (how I've been setup for 5 years). But I have tried creating a smaller catalog with RAWs on the same internal drive, but it makes no difference.
Really hoping for some help to sort this, or at least some confirmation that Adobe are aware of the issue and are looking for a fix.
Nick Church Photography