While it may seem counter-intuitive, larger image sizes (over 2 MP) can actually result in grainy, poor-quality ID card photos. Due to the large amount of data, the Photo ID card software is unable fit all of it into the printed image.
In addition, extremely large image files can actually slow down the entire program as well, as the images jam up the database. To ensure the optimal resolution for your photo ID image file, DiscountID.com recommends taking your photos with the Logitech Webcam.
For clear, focused images, the file size of the photo should be no larger than 2 megapixels.