I’ve noticed that when I’ve edited my raw files in ACR, another file appears alongside it in the folder with a .xmp suffix. What is this?
When working with most raw formats (apart from DNG), ACR doesn’t permanently alter the original raw file when you make adjustments, so it needs another way of storing the information.
These .xmp files are ACR’s way of saving the information so that next time you open the raw file in ACR it will still have all of your adjustments applied.
These are known as ‘sidecar’ files, and will normally be saved automatically when you click Open Image or Done in the ACR window.
The only time that you need to worry about these extra files is when you are moving or copying the image from one place to another, when backing-up your images onto another hard drive or if you want to edit them on another computer.
If you only copy or move the main raw file you will lose any adjustments you have made, so next time you open it in ACR or Photoshop Lightroom it will revert back to the unedited, default settings.
If you want to keep your adjustments you need to make sure that you copy both files (or copy the whole folder), or move and copy files within Adobe Bridge or Organiser, which will copy these sidecar files automatically.
These files only apply to raw files edited in Adobe software, as like raw files themselves, each software manufacturer has its own standard for storing the information.
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