Use the following recommendations to get the best performance from physical target images: Image objects should be rigid, not flexible, matt, not glossy. Small objects are good for editing by the user. Be creative in selecting objects so that they are useful, pertinent and playful.
A hard material such as cardboard, plastic or paper attached to an inflexible surface is better than a simple printed sheet of paper. The reason for this is that the flexibility of the printed paper can make it difficult to keep the object in focus. However, paper objects are easily reproducible and widespread, so you should not completely disregard them as valid targets.
Note that even if you give detailed instructions for the print format and paper quality, most users will revert to the standard of their printer, which is usually set to A4 or US Letter. To avoid these printing problems, it makes sense to store settings for books, promotional materials, packaging or posters.