To create sharp, vibrant keepsake photo books we print them at a high resolution of 300 DPI.
While you edit your photo book and place a photo in a placeholder, our creator tool will automatically give a warning (red exclamation mark) if the quality of the photo is not good enough. 

To check the DPI of your image, right-click on the image in the folder and choose "Properties". Under the tab "Details" you can find the resolution.