I ran into this problem while travelling. I wandered into a camera shop, and asked to try out a Canon 5D they had on display. I took the CF card from my 40D, put it in the 5D, fired off some shots, and then put the card back in my 40D. I quickly viewed the photos – the 40D had no problem displaying the 5D’s images, but the file numbers had changed. I didn’t notice this immediately – only that evening when reviewing the day’s pictures. The 40D was on 5000 odd, and now, all of a sudden, it was counting in the 8000 range.

I realised that this was because the 5D were on that many shots, and my 40D is set to “continuous” – it simply continued where the card stopped. While this makes no difference to the operation of the camera, the continuous file numbering is the only way I have to know how many clicks my shutter has done. So I wanted to fix it. Since I was travelling I didn’t have the tools at hand to make screenshots, etc, so I did this again on purpose, just on a smaller scale. Here’s how to fix it:

You will need a card reader for this, since the Canon DSLRs don’t show up as a storage device when plugged into a computer.

This is what the content of the card looks like:

So I renamed the last four files to follow up on the first ones and took another shot, but it was still counting in the 8000s:

Lets rename that again, just to keep things tidy:

To get pas this, I had to do the following:

1. Navigate to the fifth tab in the menu, select “File Numbering” and then “Manual reset:”

Make sure that you leave “File Numbering” set back to “Continuous:”

2. Take another shot. This will create a second folder on the card, “101CANON,” containing the new image, now numbered 0001:

Move the image(s) to the “100CANON” folder, rename them to follow up on the previous ones, then delete the “101CANON” folder, clean out your Trash/Deleted Items.

3. Put the card back in the camera, take another shot, and it will now show up correctly:

I cannot promise anything on any other EOS models, but assuming they all use the same continuous numbering method, and offer you the option of resetting the counter, it should work the same.

Happy shooting!