If you’ve connected your phone or camera to your computer as a mass storage device, you’ve probably seen this:
There are probably additional files and folders shown as well but after enough searching, you probably noticed that the pictures were buried in a folder called DCIM. Why and what does it stand for? Can it be changed to something more logical like “Pictures”?
The Japan Electronics and Information Technology Industries Association, or JEITA, has established a Design rule for Camera File systems. Section 4.2.1 of the Design rule for Camera File system DCF Unified Version 2.0 (English .PDF) (CP-3461B) establishes the rules:
The directory with the name “DCIM” directly under the root directory is called the DCF image root directory.
DCIM stands for “Digital Camera Images”.
Section 4.2.2 then goes on to elaborate how subfolders may be named. That’s why you might see a folder beneath it with the name of your camera or other information. Diddly.com has a list of some common file prefixes for different camera manufacturers.
As the Design rule for Camera File system on Wikipedia goes onto explain:
The root directory in a digital camera contains a DCIM (Digital Camera Images) directory which contains possibly multiple subdirectories with names such as “123ABCDE”, which consist of a unique directory number (in the range 100…999) and five alphanumeric characters, which may be freely chosen and often refer to a camera maker. These directories contain files with names such as “ABCD1234.JPG”, which consist of four alphanumeric characters (often “DSC_” or “IMG_”), followed by a number. The file extension is “JPG” for Exif files and “THM” for Exif files that represent thumbnails. Other file formats use different extensions. Multiple files sharing a number (even if the file extension or the four alphanumeric characters are different) are considered related and form a DCF object.
So, there’s the answer. As easy as that, a standard established by an association says that images will be found in a folder called DCIM and you’re not likely to be able to change that unless you hack your camera’s firmware. It seems like it is just something that will have to ingrain itself in our heads that the DCIM folder is where you’ll find your photos when looking at the camera through the mass storage device class protocol.