Ram maxes out on CR3 or DNG files

Hi ​@Admirable_codea75f,

Thanks for reaching out and describing this in detail. I can understand how frustrating it must be when your system gets completely bogged down. This is clearly not a case of inadequate hardware.

The behavior you're describing, RAM climbing specifically with CR3/DNG files combined with AI-powered features like Lens Blur and Masking, aligns with known performance-intensive workflows in Lightroom Classic. These features rely heavily on both system RAM and your GPU's VRAM, and the memory demands compound as you stack multiple adjustments.

Here are some targeted troubleshooting steps to try:

1. Make sure you're running the latest version (15.5).

2. The memory pressure becomes worse as more AI masks (Select Subject, Select Sky, Brush masks) are layered in the same editing session without closing LrC. Try this workflow adjustment:
Apply your basic adjustments first (exposure, white balance, tone curve)
Save and restart Lightroom Classic before applying AI-heavy features like Lens Blur.
This releases cached mask data from memory before the most demanding operations begin.

3. Go to Edit > Preferences > Performance (Windows) and check your Camera Raw Cache setting. If it's set very high (e.g., 20+ GB) while you're using AI masking on large CR3 files (~30 MB each), the cache can compete for processing memory. Try setting it to 5 GB or less.

4. Lens Blur and AI Masking are GPU-accelerated. If your laptop GPU has 8 GB or less of VRAM, these features can quickly saturate VRAM, forcing the system to spill over into system RAM, which explains your 32GB exhaustion. You can monitor this by Opening Task Manager > Performance > GPU while editing. Watch "Dedicated GPU Memory" if it hits your card's maximum, that's the bottleneck

5. Test by adjusting your GPU settings in LrC. “Use Graphic Processor > Custom > Use for Display” and Disable "Use GPU for preview Generation" Temporarily. This forces masking/Lens Blur to compute on the CPU only; it'll be slower per operation, but won't trigger the VRAM, RAM spill cascade that causes your system-wide freeze, and will confirm whether it is due to GPU VRAM or not.
 

6. Create a new test catalog, import a handful of the problematic CR3/DNG files, and apply the same edits (Lens Blur + masks). If the issue doesn't reproduce in the fresh catalog, it could indicate catalog-level corruption or accumulated mask data bloating memory during retrieval.
 

A few questions to help narrow this down further:

• Please share system info (Help > System Info) and copy & paste its contents here.

• How many images are you typically editing in a single session before the slowdown starts? Does it happen on the first CR3/DNG you edit, or only after working through several?

• Are you stacking multiple masks on a single image (e.g., Select Subject + Brush mask + Lens Blur all on one photo), or does it happen with just one adjustment like Lens Blur alone?

Looking forward to your response.

Best,
Anshul Saini

Please go to Help->System Info and paste the information it provides into your reply.