Session Sidecar files

QUESTION

What is this CaptureOne folder alongside my raws, what do the files inside do?

ANSWER

When working in a session document, any time an image is viewed Capture One will create a subfolder called CaptureOne for all the sidecar files. Keeping these alongside the raw means speedy performance and easy backup/transport. The sidecars are named the original image files' name, plus an additional extension. Let's look at what's going on.

CaptureOne/Cache/Proxies

• .cof - Focus Mask information
• .cop - Cache Preview files

CaptureOne/Cache/Thumbnails

• .cot - Thumbnails

CaptureOne/Settings###/

This folder will reflect the Capture One rendering engine version used to view the images. Here, it's 120, which is Capture One 12.

• .comask - Layer mask files
• .cos - All adjustment information
• .icm - Custom ICC Profiles (as defined in the Base Characteristics tool)

Which ones are important?

Realistically, anything in the /Cache folder can be deleted. Capture One will simply rebuild the files the next time the image is viewed in a session. 

The information in Settings120 is absolutely important as this is where anything you do to an image is stored. Since Capture One operates by proxy and never writes to the source file (the .cr2s here), anything you do is stored in these little files.