I just recently returned to LR/PS after a foray into other apps (some are decent, but Adobe is Adobe).
Anyhow, I'm debating whether to go the Bridge/ACR/PS or LR/PS workflow.
I like LR for some of the extra features, but I'm noticing that when I send an image to Photoshop, the RAM usage on my M1 iMac for Lightroom goes from 1.8gb to like 5gb. This is very strange. It's even higher that Photoshop's usage after adding a few adjustment layers.
Does anyone have a solution or explanation as to why the Ram usage has that spike?
Only offering an educated guess here, not necessarily a definitive answer. When editing an image in Lightroom Classic, the edits are only in the catalog database as metadata, and if recently edited, in the Camera Raw cache for the Develop module.
When sending that image to Photoshop, the image and the current state of edits must be rasterized to pixels, as part of being converted to a Photoshop document. That process might require a little more memory, but possibly a larger amount of memory if the pixel dimensions of the image are larger or if there are many local adjustments to compile.
It might require less memory for it to be sent to Photoshop as a Smart Object, because then the rasterization is deferred.
I haven’t actually tested those, but it’s something for you to experiment with…if the amount of memory used varies with the pixel dimensions being sent, or depending on whether it’s sent as pixels or a Smart Object.
In the long run I don’t see a concern with temporary spikes in memory usage, because when I leave a Mac running for weeks between restarts, macOS seems to recover memory regularly, flushing data not recently used so that Memory Pressure does not continue climbing and can drop back down after a while.