Lightroom CC 2015.10: Sync Activity says "Master image missing" (it's not) while over 100 % processor power is in use on MacBook Pro 2011 Core i7

  • 1
  • Problem
  • Updated 10 months ago
  • (Edited)
Running LR CC 2015.10 Sync Activity has been saying for awhile that "Master image missing" for 32 photos while those master images are just fine on the correct path (clicking the file path link on Sycn Activity window shows the photo on the Library and there are no missing original photo file errors, as seen on the attached screenshot, even though due to fixed window width and no way to scroll horizontally you can't see the full path).

At the same time macOS Activity Monitor keeps saying LR taking over 100 % processor power.

In addition Lightroom feels slow, as for example moving in menus pointing with mouse might take a second to change top-level menu or highlight menu items while moving to point different menu item.

Using Early 2011 MacBook Pro with quadcore Core i7 2.3 GHz with 16 GB memory and 70 GB free disk space on internal SSD (for system and applications), 300 GB free disk space on external SSD (for Lightroom Catalog, Previews and Smart Previews) and 500 GB free disk space on external HDD (for original NEF files).

Attached are some log files I managed to gather this morning. Last editing and work on LR was done last night and I've not done any work on LR today. This seems to happen all the time, LR using over 100 % processor power even though no work load is on LR.

Is this related to LR problems running six or more cores systems? Core i7 has only four cores but this model has eight logical processors so it shouldn't be affected, I suppose.

System Info (via Lightroom > Help menu):
Diagnostic Log for Sync Activity (via Lightroom > Preferences > Lightroom mobile > keeping Option key pressed and clicking Generate Diagnostic Log button):
Photo of anssik


  • 103 Posts
  • 20 Reply Likes

Posted 10 months ago

  • 1
Photo of Art M.

Art M.

  • 72 Posts
  • 15 Reply Likes
I have also had this "master image missing" error several times in 2015.10 LR, when the path was actually correct and previously used. New to 2015.10. Is this a LR bug or OSX issue? Well no other app that I have has this problem. Shutting it all down and reopening it always fixed it, at least temporarily.

I have also had severe slowdowns in D mode on photographs that have a lot of spot/heal edits or brush edits.

MacBook pro 2015 16gig 1TB SSD, leaving over 100gig available on hard drive, running very few other apps at the same time.
Photo of Simon Chen

Simon Chen, Principal Computer Scientist

  • 1293 Posts
  • 351 Reply Likes
Could there be a case sensitivity issue on the master image file path?
Photo of anssik


  • 103 Posts
  • 20 Reply Likes
How would that happen? I mean, I'm no programmer so I don't understand how some of the photos randomly would have problems with case sensitivity with image file path.

I managed to solve the "Master image missing" with Save Metadata to File for those photos. That doesn't make sense to me but that solved it. How could saving metadata correct missing master image file? I don't understand.

Lightroom idling but taking over 100 % processor load still exists. For few seconds it might go down to less than 10 % or so but when I just open Lightroom and do nothing with it most of the time Activity Monitor shows LR taking over 100 % processor load. There's nothing on Sync Activity anymore so I don't understand why LR takes so much processor load and makes the fans on my MacBook Pro speed up and make noise.

Here's Activity Monitors log when I've just opened Lightroom and let it idle for some minutes without any syncing happening or editing done to photos:
Here's LR Sync Log via Generate Diagonstic Log button:
Photo of anssik


  • 103 Posts
  • 20 Reply Likes
I changed to my other computer (iMac) and as I had sync problems there as well for other 18 photos (not "Master image missing" but just "Error" in Sync Activity) tried the Save Metadata to File without luck. Deleting those photos from All Synced Photographs didn't help either as those photos still had "Error" related to them and status was "Uploading" even though they did show up in LR Mobile on my iPhone so clearly they were already uploaded. So I deleted those files from LR Mobile and now there's no more errors on Sync Activity on my iMac either. I guess you can label this problem now solved.

What I still don't understand is why LR desktop keeps the sync data on the system folder and not with the Catalog file so that when keeping the LR Catalog on an external SSD (to be able to change between a desktop and a laptop computer) sync data would be current which ever computer and LR installation you are using.

Syncing is very useful and I am depending a lot to it (reviewing photos on my iPad and iPhone, doing small editing on them on-the-go and sharing Collections to others to review and download. But, all these sync issues are troubling and make me not to trust on it.

Still after solving these recent sync problems LR CC 2015.10 is utilizing over 100 % processor load even when idling (it's been now over an hour since I restarted LR desktop on my iMac and have done no work with it and it hasn't been syncing anything. I'm opening another thread for this problem as it needs to be inspected why is LR taking over 100 % processor load when idling (