Files with the MOS extension contain raw image data generated by different models of digital cameras from Leaf and Mamiya.
The MOS files contain the unprocessed or minimally processed raw data of the image sensor. Although these RAW (raw) data are larger than the JPEG files stored by the device, they are more versatile.
These sometimes called "digital negative" raw data are excellent for post-processing such as the adjustment of the colors, correction of the exposure, suitable for sharpening or noise filter. They are indispensable for professional work or things like astrophotography.
In order to convert them into an RGB image format that can be commonly used, the data must be "developed". This means that processing steps such as interpolation and exposure as well as converting to a format such as PNG, PSD, TIFF or JPEG must be performed.
However, there is no uniform raw data format. Every manufacturer has developed his own. These proprietary and often undocumented formats can only be processed by specialized software. They can contain different data, for example in different color depths, depending on the capabilities of the sensor as well as the software integrated in the camera. Manufacturers are changing their RAW formats relatively frequently, which means that program support often needs to be adjusted. Supporting the extension is not enough if the specific camera is not supported.
Most RAW files also contain metadata with information about the image and the recording conditions, in part also in the EXIF or IPTC standard.
Adobe Photoshop and Photoshop Elements support a large number of cameras with the help of the free plug-in Adobe Camera RAW (ACR). Which depends on the ACR version. However, newer versions of ACR can only be used by the latest versions of the main programs.