P: Canon tethering stopped working after updating to Lightroom Classic v15.4

Canon R6 Mark III here and it’s not working. It detects the camera and I’m able to show live view and trigger the shutter button via Lightroom, but images are never transferred to macOS. Image counter on camera keeps flashing forever, like it’s trying to save the image but never ends.

Tried the “Canon SDK for Tethering” but with that option enabled the camera isn’t detected at all in Lightroom.

I’m using Lightroom Classic v15.5 in macOS.

Subject: Canon EOS R3 Tethered Shooting and CR3 RAW Processing Issues in Lightroom Classic 15.5

Hello Adobe Lightroom Support Team,

I am experiencing a serious issue with Canon EOS R3 tethered shooting and CR3 RAW files in the latest version of Lightroom Classic.

I would like to report this issue because the behavior changed significantly after the Lightroom Classic updates.

1. Issue by Lightroom Classic Version

I have been using a Canon EOS R3 with Lightroom Classic for tethered shooting.

• Lightroom Classic 15.3.1 and earlier:
  Tethered shooting with the Canon EOS R3 worked normally without any issues. CR3 RAW files were also saved and processed correctly.

• Lightroom Classic 15.4.1:
  Tethered shooting with the Canon EOS R3 stopped working, making tethered shooting impossible.

• Lightroom Classic 15.5:
  Tethered shooting became available again, but a new and serious problem appeared: some CR3 files captured during tethered shooting are no longer being recognized or processed correctly as RAW files.

Because the problem appeared after the Lightroom version changes, I suspect there may be a regression or compatibility issue related to Canon EOS R3 tethered shooting.

2. Current Problem in Lightroom Classic 15.5

I am using a Canon EOS R3 with Lightroom Classic tethered shooting on a MacBook with an Apple M1 processor.

The camera is configured to save images as RAW (CR3) files.

Most images are captured and processed correctly as RAW files. However, some images within the same shooting session are processed as if they were JPEG files.

The particularly important point is that the affected files still have the .CR3 file extension, but their file size is similar to that of a JPEG file rather than a normal CR3 RAW file.

In other words, the file extension indicates CR3, but the file size and the way Lightroom processes the file are very similar to a JPEG.

For example:

• IMG_00108.CR3 → normal CR3 RAW file, with full RAW processing available

• IMG_00109.CR3 → .CR3 extension, but the file size is similar to a JPEG and Lightroom processes it differently, as if it were a JPEG

3. Difference in the Develop Module

For a normal CR3 file:

• Profile: Adobe Color

• White Balance: 4750 / +19

• RAW-specific processing controls work normally

For an affected CR3 file:

• Profile: Color

• White Balance: As Shot

• The Develop module behaves differently from a normal RAW file and appears to process the image in a JPEG-like manner.

I have attached screenshots comparing a normal CR3 file and an affected CR3 file.

4. Troubleshooting Already Performed

I removed the affected CR3 file from the Lightroom catalog and imported the exact same original CR3 file again.

However, the exact same problem occurred after re-importing the file.

Therefore, this does not appear to be simply a Lightroom catalog, preview, or cache issue.

5. System and Software Environment

• Camera: Canon EOS R3

• File format: CR3 RAW

• Shooting method: Lightroom Classic tethered shooting

• Computer: MacBook with Apple M1 processor

• Lightroom Classic:

  • 15.3.1 and earlier: Tethered shooting and RAW processing worked normally

  • 15.4.1: EOS R3 tethered shooting did not work

  • 15.5: Tethered shooting works again, but some CR3 files are incorrectly processed as JPEG-like files

The problem does not occur with every image. Only some CR3 files from the same tethered shooting session are affected, while other CR3 files from the exact same session work normally.

6. Request for Investigation

Could you please investigate whether this is a regression or compatibility issue introduced in Lightroom Classic 15.5?

In particular, I would appreciate it if you could investigate the following possibilities:

1. Whether Lightroom Classic 15.5 can incorrectly generate or save CR3 files during EOS R3 tethered shooting.

2. Whether RAW data is sometimes not being properly written during the tethered transfer process.

3. Whether JPEG preview data is being incorrectly saved or used instead of the actual RAW data.

4. Whether Adobe Camera Raw is incorrectly decoding certain CR3 files generated during tethered shooting.

5. Whether there is a compatibility issue between the Canon EOS R3 and Lightroom Classic 15.5.

6. Whether this is a known regression introduced in Lightroom Classic 15.5 compared with 15.3.1 or earlier versions.

The version history is particularly concerning:

15.3.1 or earlier → Everything worked normally
15.4.1 → EOS R3 tethered shooting stopped working
15.5 → Tethered shooting works again, but some CR3 files are incorrectly processed as JPEG-like files

This strongly suggests that the changes to the tethered shooting functionality may be related to the current CR3 issue.

These files were captured during professional photo shoots, so it is very important that every image captured in RAW mode remains fully editable as a RAW file.

If necessary, I can provide both:

• An affected CR3 file: IMG_00109.CR3

• A normal CR3 file from the same shooting session: IMG_00108.CR3

I would be happy to provide these files so that your engineering team can compare their internal structure and determine why the affected CR3 file is being handled differently.

Thank you for investigating this issue. I would appreciate any information regarding a known issue, workaround, or planned fix.

 

Subject line suggestion: Canon EOS R5 tethered capture: shutter unresponsive, "PC Full" error, intermittent transfer failures

Description of Issue:
During tethered capture with a Canon EOS R5, the camera's physical shutter button stops firing/responding partway through a session. The camera displays a "PC Full" error on its screen when this happens. The only way to temporarily restore shutter function is to click the shutter-release button in Lightroom's Tethered Capture panel once; the physical shutter then works again briefly before the issue recurs. In some cases, files also fail to transfer to the computer entirely, with Lightroom reporting a "file not found" error even though the camera indicates the shot was taken.

Lightroom Classic Version Number: 15.5 (Help > System Info)

OS Version Number: macOS Sequoia 15.x (Apple M1 Pro)

Camera Model: Canon EOS R5 (original, not Mark II), firmware 2.2.1

Step-by-Step Reproduction Instructions:

1. Connect Canon EOS R5 via USB-C tether cable directly to Mac (tested on all 3 available ports, no hub/dock)
2. Start Tethered Capture in Lightroom Classic with destination set to a local folder, Metadata set to None
3. Shoot in Single Shot drive mode (also reproduced in Low Speed Continuous)
4. After a number of shots, camera displays "PC Full" and the physical shutter button stops responding
5. Click the on-screen shutter button in Lightroom's Tethered Capture panel once - camera responds and shutter works briefly again
6. Issue recurs after further shots

The Expected Result:
Camera should continue to fire normally via the physical shutter button for the full duration of the tethered session, with all files transferring successfully to the computer.

The Actual Result:
Physical shutter becomes unresponsive, camera shows "PC Full," and files intermittently fail to transfer with a "file not found" error in Lightroom, despite the camera indicating a successful capture.

Troubleshooting already completed (issue persisted through all of the following):

• Tested 3 different tether cables (different brands)
• Tested 3 different memory cards
• Tested multiple camera batteries
• Tested all 3 USB-C ports directly, no hub/dock
• Disabled camera Wi-Fi and Bluetooth (both were previously enabled)
• Confirmed macOS Privacy & Security settings: Lightroom Classic Full Disk Access OFF, Removable Volumes access ON
• Confirmed no Canon EOS Utility installed or running in background
• Tested with no memory card in camera (writing to computer only) - issue still occurred
• Tested with/without exposure compensation, Servo AF, and Single Shot AF - no difference
• Tested destination on internal HD and on an external drive - issue occurred on both
• Confirmed files arrive as native .CR3 (not converted to DNG)
• Switched drive mode from Low Speed Continuous to Single Shot - issue still occurred
• Updated camera firmware from 2.1.0 to latest 2.2.1 - issue persisted
• Updated Lightroom Classic to latest version 15.5 - issue persisted
• Confirmed GPU acceleration settings on Auto (M1 Pro, full acceleration supported); increased Camera Raw Cache size from 5GB to 20GB and purged cache

Partial workaround found:
Toggling ON "Use Canon SDK for tethering" in Lightroom Classic preferences (previously OFF) significantly improved reliability - files now transfer consistently with no more "PC Full" or "file not found" errors. However, a noticeable delay/buffering period now occurs before each incoming image displays in Lightroom, even though the file has already been received successfully.

Additional questions:

1. Is this a known issue with Canon R5 tethering in recent Lightroom Classic versions?
2. Was the default value of "Use Canon SDK for tethering" changed in a recent update? This could explain why tethering worked reliably for a long period and then degraded without any change on my end.
3. Is there a recommended fix for the buffering/display delay now that SDK tethering is enabled?

Thank you.

Subject: Canon EOS R5 tethered capture: shutter unresponsive, "PC Full" error, intermittent transfer failures

Description of Issue:
During tethered capture with a Canon EOS R5, the camera's physical shutter button stops firing/responding partway through a session. The camera displays a "PC Full" error on its screen when this happens. The only way to temporarily restore shutter function is to click the shutter-release button in Lightroom's Tethered Capture panel once; the physical shutter then works again briefly before the issue recurs. In some cases, files also fail to transfer to the computer entirely, with Lightroom reporting a "file not found" error even though the camera indicates the shot was taken.

Lightroom Classic Version Number: 15.5 (Help > System Info)

OS Version Number: macOS Sequoia 15.x (Apple M1 Pro)

Camera Model: Canon EOS R5 (original, not Mark II), firmware 2.2.1

Step-by-Step Reproduction Instructions:

1. Connect Canon EOS R5 via USB-C tether cable directly to Mac (tested on all 3 available ports, no hub/dock)
2. Start Tethered Capture in Lightroom Classic with destination set to a local folder, Metadata set to None
3. Shoot in Single Shot drive mode (also reproduced in Low Speed Continuous)
4. After a number of shots, camera displays "PC Full" and the physical shutter button stops responding
5. Click the on-screen shutter button in Lightroom's Tethered Capture panel once - camera responds and shutter works briefly again
6. Issue recurs after further shots

The Expected Result:
Camera should continue to fire normally via the physical shutter button for the full duration of the tethered session, with all files transferring successfully to the computer in a decent time as before.

The Actual Result:
Physical shutter becomes unresponsive, camera shows "PC Full," and files intermittently fail to transfer with a "file not found" error in Lightroom, despite the camera indicating a successful capture.

Troubleshooting already completed (issue persisted through all of the following):

• Tested 3 different tether cables (different brands)
• Tested 3 different memory cards
• Tested multiple camera batteries
• Tested all 3 USB-C ports directly, no hub/dock
• Disabled camera Wi-Fi and Bluetooth (both were previously enabled)
• Confirmed macOS Privacy & Security settings: Lightroom Classic Full Disk Access OFF, Removable Volumes access ON
• Confirmed no Canon EOS Utility installed or running in background
• Tested with no memory card in camera (writing to computer only) - issue still occurred
• Tested with/without exposure compensation, Servo AF, and Single Shot AF - no difference
• Tested destination on internal HD and on an external drive - issue occurred on both
• Confirmed files arrive as native .CR3 (not converted to DNG)
• Switched drive mode from Low Speed Continuous to Single Shot - issue still occurred
• Updated camera firmware from 2.1.0 to latest 2.2.1 - issue persisted
• Updated Lightroom Classic to latest version 15.5 - issue persisted
• Confirmed GPU acceleration settings on Auto (M1 Pro, full acceleration supported); increased Camera Raw Cache size from 5GB to 20GB and purged cache

Partial workaround found:
Toggling ON "Use Canon SDK for tethering" in Lightroom Classic preferences (previously OFF) significantly improved reliability - files now transfer consistently with no more "PC Full" or "file not found" errors. HOWEVER a noticeable delay/buffering period now occurs before each incoming image displays in Lightroom, even though the file has already been received successfully.

Additional questions:

1. Is this a known issue with Canon R5 tethering in recent Lightroom Classic versions?
2. Was the default value of "Use Canon SDK for tethering" changed in a recent update? This could explain why tethering worked reliably for a long period and then degraded without any change on my end.
3. Is there a recommended fix for the buffering/display delay now that SDK tethering is enabled?

Thank you for your help.

Bonjour,

J’utilise le mode connecté via Wifi. Sur Lightroom classique il ne fonctionne plus depuis la version 15.4.1. J’ai installé la version 15.5 pareil, ne fonctionne pas.

J’utilise le R5 mark2

Eos utility détecte l’appareil photo mais Lightroom ne fait plus le lien. Je suis obligé de rester sur la version 15.3.1.

Merci pour vos retours

Greetings all,  
 
A new update for the Adobe Photography products has been released.  The August release (x.5) contains an update regarding this issue.  

If you do not see the update in your Creative Cloud Application, you can refresh it by pressing  [Ctrl/Cmd]+[Alt/Opt]+[ R ]. 

Note: It may take up to 24 hours for your update to be available in your Creative Cloud app.
 
Thank you for being so patient.  

Hello,

I’m having the same issue with my Canon R1. No photos are being written to the hard disk on my MacBook Pro, only to the CFExpress cards. 

Having this same issue 

Still getting terribly unreliable tethering…? Reverted back to Canon SDK and it seems a little better and I then tried going back to the LR Native PTP and it doesn’t now want to work at all with the new PTP protocol, so, hmm. MacBook Pro 15, latest Tahoe build, Canon R5 Mk II with latest firmware.

You really really need to just go reverse engineer Capture One’s tether code as this is and always has been terribly poor in Lightroom.

I am experiencing a tethering issue with Lightroom Classic and my Canon EOS R6 Mark II.

My setup:

• Canon EOS R6 Mark II
• MacBook Pro M5 Max (128GB RAM)
• Tether Tools Pro USB cable
• RAW shooting
• Internal SSD with plenty of free space

During tethered shooting, Lightroom works normally at first, but after around 29 RAW photos, the camera shows "PC FULL" and stops shooting. This also happens with JPEG files.

I have tested the same camera and cable with Canon EOS Utility, and tethering works perfectly without any issues. I also tested the RAW files in Canon Digital Photo Professional 4, and everything works normally.

I increased Lightroom Camera Raw Cache to 50GB, checked my SSD storage, and confirmed that my computer has sufficient resources, but the issue still happens consistently.

Since the problem only occurs in Lightroom Classic, I believe it may be related to Lightroom's tethering process or buffer management. I have lastest version of Lightroom and camera firmware.

Could you please help me resolve this issue?