File numbering and naming

Canon digital cameras save your image files in folders on the memory card(s) installed in the camera's slot(s), and the files and folders are automatically numbered to make them easy to identify. The file numbers start at 0001 and go up to 9999 before a new folder is opened and the numbering starts again from 0001. The folders are given numbers running from 100 to 999.

EOS digital cameras offer you a choice of file numbering systems: Continuous or Auto Reset. Which you choose depends on how you like to work, but Continuous is the best choice for most photographers.

Continuous numbering: As the name suggests, this numbers each new image in sequence from 0001 to 9999.

If you remove a memory card from your camera and replace it with a fresh, newly-formatted card (or switch target cards), the sequence will continue. So if you had been using folder 100 and the last number used was 0051, then the camera will create folder 101 on the new card and number the images saved to it starting with 0052.

The advantage of this system is that, until you reach image 9999, every file has a unique number. This can help avoid problems when you download the images to a folder on your computer, but it might not be ideal for your set-up. For instance, if you use two EOS non-pro digital cameras, you will have multiple files with the same file names. The safest way to deal with this is by batch renaming, which we'll look at shortly.

Auto Reset: When this option is selected the camera returns to the start of the number sequence (100 for the folder, 0001 for the file) each time you insert a newly formatted card into the camera. It means that you will get files with the same file names every time you change card. Again, the solution is batch renaming.

If the memory card you insert into the camera already contains image files, the numbering sequence in both Continuous and Auto Reset modes will continue from the highest file number on the card, rather than continuing the camera sequence.

EOS professional cameras offer a third numbering system called Manual Reset. This allows you to create a new folder on the card when you want it, rather than every 9,999 images. This can be useful if you want to separate images taken at different times or of different subjects.

If you want to know the folder and file number of the shot you have just taken, press the playback button on the back of the camera and, if necessary, the Info button. The image will appear on the LCD screen with the two numbers in the top right.

The names assigned to image files vary slightly with different EOS cameras. Here's a guide to what you may see, and what it means.


IMG_0001.JPG

JPG shows that image has been saved in JPEG format. IMG is short for image, and it is followed by the four-digit file number. This means that the highest file number within a folder is 9999. After this, a new folder is created on the card and the numbering starts again. This means you should be careful downloading from multiple folders to the same location on your computer, because files may have the same name. To help prevent images being overwritten accidentally, use the Rename tool in Canon's Digital Photo Professional (DPP) software – see the section about file renaming below.


_MG_0001.JPG, _XXX0001.JPG

An underscore at the start of a JPEG file name indicates that the image was shot using the Adobe RGB colour space. When sRGB is set, there is no underscore. This occurs automatically on any camera where the colour space can be selected, so the rest of the file name may vary, and it enables software as well as users to simply identify what colour space was used and open the image with the correct colour profile.


XXXX0001.JPG

EOS professional digital cameras use a four-character camera code as the prefix to the file name. This code is unique to the individual camera and is preset by Canon during manufacture, but with more recent cameras – the EOS 5D Mark IV, the EOS-1 D series, and the EOS R5 – it can be customised by the photographer, and changed as frequently as you wish. So you might, for example, wish to use a custom code for a particular shoot, such as 21NY for your 2021 shoot in New York. See your camera manual for details. Note that you cannot set an underscore as the first character, because that is reserved for shots taken using Adobe RGB, as noted above.


XXXL0001.JPG, XXXN0001.JPG, XXXM0001.JPG, XXXS0001.JPG, _XXL0001.JPG, _XXN0001.JPG, _XXM0001.JPG, _XXS0001.JPG

An L, M, N or S in the file name indicates that the camera’s file size was set to L = Large, M = Medium1, N = Medium2, S = Small.


CRW_0001.CRW, XXXX0001.CR2, XXXX0001.CR3

These are the Canon RAW files for still images. EOS cameras released since 2018 use the newer CR3 format.


XXXX0001.HIF

The HIF extension indicates that the image is an HEIF (High Efficiency Image File Format) file. This is a newer file format with more efficient file compression than JPEG. It has 10-bit colour rather than the 8-bit of a JPEG.


MVI_0000.MOV, XXXX0001.MP4

These are movie file formats. Most EOS cameras record in the MP4 format. Cameras that record 4K footage might use various container formats including .MXF or .MTS.


XXXX0001.CRM

This is the Canon RAW video format, which means that the footage has much greater scope for post-capture adjustment and grading. Some cameras also use .RMF.

CRW_0001.THM, CR2_0001.THM

When you shoot a RAW file, the camera also creates a very small file that produces the preview image you see on the screen on the back of the camera. The small image is called a thumbnail, which is abbreviated to THM.


MVI_0000.THM

These files are the static thumbnail images associated with some movie files.


XXXX0001.WAV

Some cameras with a built-in microphone – including the EOS-1D series, EOS 5D Mark IV (with updated firmware) and EOS R5 – can record up to 30 seconds of commentary to be attached to each image. The sound is stored as a WAV (waveform audio) file with exactly the same name and number as the image it relates to.

You might also come across a folder named CANONMSC, which is short for Canon Miscellaneous. Inside, you will find files that end with the .CTG extension. Close this folder and leave it alone. These files contain data that helps with the storage and maintenance of the image files on the memory card.

Once an image file is transferred to your computer, it’s a good idea to store it in a folder with a name that is relevant to the images. For example, if you've shot a set of portrait images, it makes sense to store them in a folder with the name of the person in the images and the date of the shoot. However, the image files will still have names like IMG2813.JPG.

Canon's Digital Photo Professional (DPP) software makes it easy to rename an entire batch of files in one go. Here's how:

1. In the main window, select the images that you want to rename.
2. Go to the Tools menu and select Start Rename tool.
3. Use the File name dropdown options to set the naming structure of your images, with the option of typing in your own custom name (User-selected string).
4. Use the Extension dropdown options to specify whether to keep the current file name extension (upper or lower case) or change case.
5. Select your preferred sorting order.
6. If you included a sequence number in your file names, set the first number and tick Save sequence number to instruct DPP to remember the last number it used and start future renumbering from there.
7. If the shooting date is included in your file name, select your preferred date structure.
8. To ensure it’s easy to match up JPEGs and RAW files that were shot simultaneously, select Same file name for RAW+JPEG images.
9. If you want to copy the images to another folder, click the Copy and Rename box and then click on Browse to select the destination
10. Check that the panels at the bottom are displaying the correct originals and you're happy with the modified file names, then click Execute to perform the renaming process.