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Issue with CF Card on 5D Mark III

I did a photo shoot this weekend, using my 5D Mark III. It holds two cards, so I used the SD card slot for large JPGs and the CF card slot for raw files (I've been shooting this way for years without issue). Before shooting, I formatted both cards inside the camera.

After the shoot, I shared the SD card with my client to preview on her laptop. Everything looked good. I held off on removing the CF card until this morning when I arrived home. When i plugged it into my Mac, however, the computer wasn't recognizing the card, which was odd (the SD card operated as expected, so I downloaded the large JPGs). 

When I put the CF card back into the camera, it said "Card cannot be accessed. Reinsert/change the card or format card with camera." I tried two different CF cards in the camera. One immediately said the same message, the second CF card worked just fine. 

I looked into the CF card slot with a flashlight and all the pins look normal - nothing bent. None of the CF cards are locked. Any idea what is going on here? Are my raw files gone?



This might help...


Best of all it's free.  I'm recommending it because I've used it before successfully, many times.  Let me know how it goes.



Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8
~CarePaks Are Worth It

Thanks, Shadowsports. Before getting your reply, I sent an email to the CF card company (Transcend). They got back to me right away and recommended I run a trial version of EaseUS Data Recovery Wizard for Mac. Thankfully, it found my raw files!


While I would have preferred to retrieve my missing 300+ raw files for free, it was the best $90 investment I could have imagined. It's just not the same trying to edit JPGs of headshots via Lightroom. 


I also get to send the CF card back to Transcend for a new one as these are guaranteed for life. 

$90 is a small price to pay as you said.  EaseUS is a great software developer known primarily for their partition management software.  Over the years they have expanded into the back up, data recovery and file utility space.  Very happy you got your raw files back. 

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8
~CarePaks Are Worth It


Hello tmtrad, 

We recommend downloading both media cards with a USB card reader.  Once you've cleared both cards of all photos you will want to format the card in the camera to see if this issue persists. 

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Good idea. I typically download all data by putting my media cards into a card reader. Unfortunately, the CF card was not being seen via the card reader (to be more specific, it's a firewire card reader). I rarely download the content on the SD card as it is typically a "just-in-case I need it" card.


I have another shoot tomorrow. I'm going to switch the order (raw files to the SD card, JPGs to the CF) as the SD card seems to be a little faster and more reliable.