Why preview generation can be slow

Preview generation during import or opening a catalog/session can take longer than expected for several common reasons. In most cases, this is related to performance settings, file location, or the size and number of images being processed.

Common reasons for slow preview generation

1. Large or high‑resolution files
   High‑resolution RAW files take longer to process. The more images you import or select at once, the longer preview generation will take, especially during the first import.
2. Previews stored on network or external drives
   If your images are stored on a network drive or a slower external drive, Capture One must wait for data to load before it can generate previews. Network latency can significantly slow this process. Check suggestions on how to best use catalogs/sessions with external drives here: Sessions vs Catalogs in Capture One: how they work and where to store them

3. Preview size set too high
   If the Preview Size in Preferences is larger than your display resolution, Capture One needs more time to generate each preview. Setting the preview size higher than necessary can reduce performance.

   

4. Previews regenerating repeatedly
   Previews may regenerate if the cache preview size is incorrect, the image metadata changes, or timestamps do not match. This can make browsing images feel slow.
5. System resources in use
   Preview generation competes with other tasks, such as imports, exports, or background adjustments. Limited CPU, disk speed, or memory can slow down the process.
6. Adjustments enabled on import
   Imports and previews can be slower when adjustments are enabled on import, because Capture One applies processing to each image as it is imported.
    

What you can do

• Set the Preview Image Size to the recommended value in Preferences>Image. 
• Store catalogs and images on fast local storage when possible and reference images from an external location. See more here: What is the difference between a referenced and a managed Catalog?
• Disable any adjustments like styles or presets during import in the Import window>Adjustments.
• Let preview generation finish before starting heavy editing.

Once previews are generated, browsing and editing images becomes much faster.