R5 failed to write to memory card

[lsphoto]

Hello,

I'm new to this forum so bear with me if I mess something up.

Today I had a photo session (a school) with my R5, which is set to simultaneously write to two memory cards.  I shot for two hours in the morning with no issues.  In the afternoon, I shot for about 30 mins when I noticed that my camera was suddenly slow - struggling to focus and it was struggling to write as fast as I was shooting - I would shoot then look at the screen and see a "buffer full" message. After a few minutes of this slow-down, I replaced the battery. It was still slow so I replaced both memory cards and that fixed the problem. The issues resolved.

When I checked the images later I discovered that some of the photos I shot were never recorded. I was shocked -- they were missing from both memory cards -- the backup card slot didn't prevent me from losing photos.

This is what I think has happened: The photos are missing from the first set of memory cards, not the second, and the timestamp on the files coincides with when I think I swapped the battery. So I think that's what did it.

I'd like to know if this is a known problem with the R5. It's very strange because from the timestamp on the image files I can see that the card didn't record for about three minutes. It doesn't seem normal for images to take that long to write to a card.

Questions:

- Is this a known problem, that images can sometimes take a long time to write on the R5?

- But if images shouldn't take long to record: as I said, I noticed a slow-down at one point, so I wonder if this means it was a defective card?

I used an EOS R5, Canon battery, Sandisk CF Pro card, Sandisk SD card. I was shooting in high speed continuous mode. I buy my memory cards from B&H or Adorama; no Amazon purchases.

Thanks,

LS

[shadowsports]

Greetings ,

The conditions that you were shooting under do not sound abnormal.  One thing to note, frame rates, continuous high speed shooting can decrease as the battery level decreases.  So you cannot shoot continuously at high speed when the battery gets very low.  The camera's ability to write to the cards will also slow.  How old is the battery you were shooting with? Was it Canon brand or other?

Do you regularly format your cards in camera before using them?

What firmware version are you running on the camera?

What brand and model lens or lenses?  Are you using any adapters? If so, what brand.  

Are you using any special folders, file naming convention, etc.

Cards can fail. It happens, but is pretty rare.  

It might be any one or a combination of the above factors.

[lsphoto]

Hi,

The battery I was shooting with was relatively new (purchased in June 2024).  Also, I replaced the battery between the morning and afternoon session.  Then, when I encountered the problem in the afternoon, I replaced the battery with the original (half full) battery that I had started in the morning session.  Both are Canon batteries - one purchased from Canon directly; the other from Adorama.

Yes, I format the cards in camera after using them and yes, I had formatted these cards prior to the session today.

I was using the Canon RF 28-70 L F2.0.

No special folders or naming conventions.

Fwiw, the memory cards were also relatively new, purchased in June and/or July 2024.  Purchased from Adorama, not Amazon.

The only thing I'm not sure about is the firmware - it hasn't been updated since maybe July 2024.

The problem is not so much why the camera started slowing down - I mean, that is not ideal, but that's why I have backup batteries and memory cards - but rather, how it could be that replacing the battery could cost me 3 minutes of shooting time / 200 files to not be written to the cards.  I know that's a high volume in a short amount of time, but again, I was shooting multiple students very fast and frankly, that's what my job is, so I need my gear to be able to handle that and I've never had this problem before!

[lsphoto]

You can see the missing files