Browsing RAW Files
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 Free you don't have to develop your RAW files to browse your photos because ACDSee Free does some basic preprocessing for you.
If there is a thumbnail of the photo embedded in the RAW file, ACDSee Free displays it in Browse mode. Sometimes the quality of an embedded thumbnail is poor, so ACDSee Free initially displays embedded thumbnails in Browse 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 Browse mode, click Tools | Options, select File List, and then uncheck the Generate high quality thumbnail checkbox.) If there is no thumbnail of the photo embedded in the RAW file, ACDSee Free quickly creates a high-quality thumbnail to display in Browse mode.
Turning off the Generate high quality thumbnail option will increase display speed but will reduce the accuracy of thumbnails for RAW images.
Once generated, the thumbnails are stored in the ACDSee Free database to speed up retrieval and display time for later browsing.