This article is for those who read our article on what to do if Capture One is starting slowly and want to know more about the technical background.
The Technical Explanation
Capture One Pro works around the concept of sessions. Whenever you open Capture One Pro it opens a session. Most of the time C1 Pro will open the session which was open when C1 Pro closed.
“Sessions” help Capture One (and the user) keep organized by keeping track of the following folders:
- The currently selected folder
- The current Capture Folder
- The current Move-To Folder (aka “selects”)
- The current Output Folder
- The current Trash Folder
- Any folder in the Session Favorites
- The contents of any Session Albums
- The most recent folders you have browsed to
For each of the above folders it keeps track of the following information:
- The sort type (name/date/rating etc)
- What images are currently selected (if any)
- How each folder in the session is being sorted (name/date/size etc)
Note that this list does NOT include any of the adjustments to your raw files (e.g. that you pushed Image XYZ0001.cr2 by 1 stop). Those changes are not contained in the “session” but are instead saved as a sidecar folder called “Capture One” next to the raw file.
In addition while browsing between folders Capture One maintains the cache/proxy data on the raw files of any given folder as long as it’s open or as long as there is available ram for it to do so. That way when you switch from “Folder X” with 300 raw files and “Folder Y” with 300 files for the first time it may take 10 seconds for that folder to load but thereafter it takes less than a second to switch back and forth.
All of this allows Capture One to very quickly access the folders that are relevant for the job at hand while ignoring and not spending overhead on folders involved in previous jobs. When you start a session or open a session you are telling Capture One to spend all of it’s attention and resources on the folders related to that job.
So if Capture One is taking unusually long to open it can often be related to a problem with a session file. Either the session file has become overly bloated or there is some “issue” with it. We’ve seen this happen most often with customers who don’t use the session system, but rather always open the default session and manually navigate to the folder they want to view. Over time this will cause Capture One to launch slower and slower until it’s nearly unbearable.