Lightroom Classic CC 7.3 (and 7.3.1) update slowed down my iMac and made fans spin at full speed

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  • Updated 2 years ago
  • (Edited)

I have a late 2017 iMac with an i7 4.2GHZ, top of the line graphic card and 40 GB of RAM, and the fans will kick at full speed every time I'm working in LR, even with 1:1 previews and smart previews built beforehand. Strangely, that issue disappeared with LR 7.2 to return in 7.3. That doesn't happen with any other software. I've read in other threads that it might be an i7 Kaby Lake issue with LR, but if the problem was solved in version 7.2, what happened for the issue to come back again with version 7.3? One thing is for sure. Lr 7.3 (and 7.3.1) is much slower especially in Develop mode and the fans are kicking at full speed. I have Sync, Face Detection and Address Lookup always paused, so no issue there. For example, I just tried to move the exposure slider and the CPU percentage went up to 605% (see attached screenshot) and the fans just fired up at full speed, even with GPU acceleration turned on and off. That's what I think it's not normal and it was an issue that I've only had in version 7.0, 7.1 and now in 7.3. Version 7.2 was the only one that seemed to fix the issues, the one where Intel helped Adobe.

I understand that Lr needs a lot of processing power and that produces more heat because of all the transistors of the CPU and GPU, especially on the retina iMac and MacBook Pro and that Adobe spent the last years trying to make it faster and addressing all the user concerns. But if the latest Apple computers use even more powerful graphics cards, more powerful processors and faster RAM, shouldn't Lr be faster and use all that power to run smoothly? How come a lower spec 2015 retina iMac runs faster and without issues than a late 2017 top of the line iMac with 40GB of faster RAM? And how did all those issues disappear in version 7.2 to reappear in version 7.3? Editing was a breeze and now it's a real pain.  C'mon Adobe, figure this out ASAP, please.
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Nuno Ferreira

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Posted 2 years ago

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John R. Ellis, Champion

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As we discussed in the other forum, the bad performance you're experiencing may be
unrelated to the CPU usage. 

LR 7.3.1, LR 7.2, and LR 6.14 (2015.14) on my MacBook Pro Retina all use a similarly high amount of CPU when adjusting the exposure rapidly back and forth for about 5 seconds.  LR 7 uses more than 700%, while LR 6 uses about 600%.  But I've never experienced any performance problems, thankfully (though the fans run constantly).

It would be interesting to see if others with good performance see similarly high CPU usage. If they do, then we all have high CPU usage, but some have bad performance and some have good performance.

Here are the CPU graphs, showing me first moving the exposure slider with the GPU enabled for 5-6 seconds, then with the GPU disabled:

LR 7.3.1

LR 7.2

LR 6.14

Details: MacBook Pro Retina, 15-inch, Mid 2015, 2.8 GHz Intel Core i7, AMD Radeon R9 M370X. Macos 10.13.4.
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Carlos Cardona

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Try givingyour Mac the "once over"! Run the free Onyx (, reboot. (In Onyx just run everything in the Automation tab). Also run Disk Warrior if you can ($120), (, reboot. If you can’t do Disk Warrior, at least run First Aid from Disk Utility. Also just doing a "Safe Boot" can clear out caches (restart, hold down shift until you see "Safe Boot" on the screen).

Also try launching Lightroom from your other (admin or test) account, with a new catalog, as a test. Does it run OK then, or still max out the CPU? If it does run OK it may be a corrupted preference in your User/Library. Check The Lightroom Queen site for instructions on how to reset your preferences ( If that doesn't work you could try deleting that entire Adobe folder (reboot), or use App Cleaner to completely delete everything Adobe and reinstall it from scratch (LAST RESORT!)
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Robert Somrak, Champion

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Seems odd that the CPU load is higher with the GPU enabled. I would have expected the opposite
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John R. Ellis, Champion

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GPUs aren't very flexible. In exchange for getting high-performance bulk computations, the CPU must convert the data from LR's internal representation to a representation more amenable for high-speed processing in the GPU, then convert the results back.