What is the easiest way to download all photos in DropBox to your desktop computer?

Hello bmcbath2, there are several ways: 

1. If your photos are organized in folders, you can download those folders by logging into Dropbox web. The limitation of downloading an folder is that the folder must not be larger than 20 GB, and contain less than 10,000 files. If you have larger folder, or more than 10,000 files in a folder, you may download them by parts or use desktop sync (2). 
2. You can install the desktop app to sync the Photos locally. You may use selective sync to download the photos folders only. 
3. If your photos are scatted across diffrent folders, you may go to the Photos tab, scroll down to the bottom, then select the checkbox next to timeline, it will allow you to download all the photos at once. However, this method won't work if you have more than 10,000 photos or the total size is more than 20 GB.