Please note this feature has been partially disabled as of version 5.4.2 due to crashes and will be put back as soon as a resolution can be found.
When the dialog is first accessed, only the 'Acquire/Open Image' section is available in which you can open an image using the 'Open...' button.
Scanner/Camera Image (TWAIN) dialog box
Having opened an image, it will appear in the preview area on the left of the dialog box:
Scanner/Camera Image (TWAIN) dialog box after opening
In the 'Image Options' section, you can now adjust the quality (a higher number will result in a larger file), the Sub sampling and whether the image is saved as greyscale. There also four buttons in this section, which do the following:
Once you set the options for your image, you can either click on the 'Add into NoteBook' button to add the image as a page, or you can click on the 'Save As...' button to save the image as a JPEG file. When clicking on the 'Add into NoteBook' button, the page will automatically select itself allowing you to view it.