There are essentially four ways that you trigger an augmented reality experience using a mobile app:
1. Using a product that you have to buy to access the AR content. Examples of this would be the new Merge VR Cube, the 4D+ cards from Octagon Studio and the augmented reality puzzles from Ravensburger.
2. Using a printable marker that you download from the developer. These are usually free but you will sometimes have to pay for specific experiences within the related app. Examples of this include the Quiver colouring pages and ZooKazam.
3. User generated triggers - the user creates their own trigger using an image or object. Examples of this include Aurasma, Zappar and Blippar.
4. Without any trigger - the experience works without a target. Examples of this include the Dinosaurs Everywhere app and Gabsee.
If you're using a physical product you are are not really able to manipulate the target marker but if you are working with an AR app that uses a printable marker, you can actually alter the scale of the target to create specific effects. As long as the integrity of the marker image is maintained, you can shrink or enlarge it and still access the content.
I tested this for the first time in 2015 using the universal Arloon trigger. I wanted something that I could have in my pocket and pull out on the spot at conferences I was presenting at (almost like an augmented reality magic trick.) I chose the Arloon trigger as it worked across all of the Arloon apps and thus would allow me to show a greater range of content.
I kept testing and ultimately found that I could shrink the Arloon trigger down to just a few square centimeters and it would still work. I printed a few copies of it on white card and always had a few tucked in my wallet for conferences. During a recent visit to Eon Reality here in Dubai, I noticed that their marker for the amazing AVR Creator is actually on their business cards!
This highlighted a couple of additional benefits for me that I took into the classroom. Firstly, by shrinking the targets I could fit multiple copies onto a single sheet of A4 paper - thus saving paper and reducing my printing costs. It also meant that they were small and plentiful enough to be given to students. I would have them stick the triggers into their books next to related work. This way they could access the experience again at home, perhaps with family.
(side note - I have not put anything bigger together on VirtualiTeach about Arloon as they seem to have gone out of business and therefore I am not sure if their apps will survive the upcoming iOS update)
You can also significantly enlarge a target marker, though you may require professional printing facilities depending on the scale you choose. The one thing you must be aware of here is that the marker must not become blurred or it will no longer be recognised by the app. Trial and error is the answer but as long as the marker is of a decent size, you should be able to go quite large...
The advantage of a supersized marker is that it can be viewed by a larger group of students simultaneously. Though most current AR apps don't offer a true multi-user experience (Eon AVR being the key exception) this can create a similar effect as they all view the content from different angles at the same time. It definitely beats having them jostle for position around a marker!
Larger markers can be stored and reused with subsequent classes. Bear in mind that laminating markers is not usually a good idea. Lamination adds a shiny, reflective sheen to the paper which will often prevent the marker from working. My advice would be to print of card if you have it available and store any markers you wish to reuse somewhere safe when not in use.