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

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?

I’ve been getting the same error since upgrading LR to 15.4.1, R6, MacBook Pro, 

I downgraded to the previous LR & no problems, so its definitely the newest LR update.

Description of Issue Canon EOS R6 Mark III cannot be detected by Lightroom Classic for tethered capture. Using the same Mac, the same USB cables, and the same Lightroom installation, Canon EOS R3 and EOS R5 work perfectly. The EOS R6 Mark III has never worked with Lightroom Classic since it was purchased. Lightroom Classic Version 15.4.1 Camera Raw 18.4 Operating System macOS Sequoia 15.7.1 Computer Mac Studio (M1 Ultra) Additional verification was also performed on: MacBook Pro (M2) Lightroom Classic 15.2 Camera Raw 18.2 Symptoms When I select: File > Tethered Capture > Start Tethered Capture Lightroom displays: "No camera detected." At the same time, the EOS R6 Mark III repeatedly disconnects and reconnects, and the camera LCD continuously flashes as if the USB connection is being reset. Important observation Apple Image Capture recognizes the EOS R6 Mark III immediately and remains connected without disconnecting. Only Lightroom Classic causes the repeated USB reconnect behavior. Environment Camera: Canon EOS R6 Mark III Firmware 1.0.2 Comparison cameras: Canon EOS R3 Canon EOS R5 Both R3 and R5 work perfectly using the identical setup. USB cables tested: - Tether Tools USB-C 5m - Cable Matters USB-C 5Gbps 7.5m Both cables work perfectly with R3 and R5. Troubleshooting already completed - Canon SDK enabled - Canon SDK disabled - USB Application = Image Import / Remote Control - Wi-Fi disabled - Bluetooth disabled - EOS Utility not running - macOS recognizes the camera in Image Capture - Two different Macs tested - Multiple Lightroom Classic versions tested - Multiple USB cables tested Expected Result EOS R6 Mark III should be detected for tethered capture exactly like EOS R3 and EOS R5. Actual Result Only EOS R6 Mark III fails to connect. Lightroom repeatedly resets the USB connection and never detects the camera. Question Could Adobe Engineering please confirm whether this is a known compatibility issue with the EOS R6 Mark III? If additional logs or testing are required, I would be happy to provide them.

Because the same Mac, same USB cables, and same Lightroom installation work perfectly with EOS R3 and EOS R5, this issue appears to be specific to the EOS R6 Mark III.

Not sure if this will help anyone with the current update but when I was having tethering errors with previous LR Classic updates, I stumbled across a workaround that got me connected. Straight into File/Tethered Capture/ Start Tethered Capture would never connect but if I followed these steps, it would tether correctly.  

Camera connected and turned off (mine is a Canon R62)

File/ Import Photos and Video

Turn the camera on and observe the camera’s name pop in on the left side

Hit Cancel on the Import Screen

Then, select Tethered Capture/ Start Tethered Capture

I had a session today - first time with the new update - and I did all this from habit and it worked fine.  

Macbook Pro M4 with Sequoia 15.6, Canon R62

Hope it helps someone!