Because a RAW file is similar to a negative, it is necessary to develop, or process it, before it becomes visible. It would be very inconvenient if you had to develop all of your RAW files before you could browse your photos. In ACDSee Pro you don't have to develop your RAW files to browse your photos because ACDSee Pro does some basic preprocessing for you.
If there is a thumbnail of the photo embedded in the RAW file, ACDSee Pro displays it in Manage mode. Sometimes the quality of an embedded thumbnail is poor, so ACDSee Pro initially displays embedded thumbnails in Manage mode, then it creates and displays a higher-quality thumbnail. You can see this happening if you look in the Status bar at the bottom of the window.
If you find that it takes too long to display the higher-quality thumbnails, you can turn off that option. (In Manage mode, click Tools | Options, select File List, and then clear the Generate high quality thumbnail checkbox.) If there is no thumbnail of the photo embedded in the RAW file, ACDSee Pro quickly creates a high-quality thumbnail to display in Manage mode.
Turning off the Generate high quality thumbnail option will increase display speed but will reduce the accuracy of thumbnails for RAW images.
ACDSee Pro also searches the database to see if you have developed a RAW file. If it finds develop settings for the RAW file, it uses those settings to display an accurate thumbnail in Manage mode.
Once generated, the thumbnails are stored in the ACDSee Pro database to speed up retrieval and display time for later browsing.