How does AirPrint (on iOS) decide what printer settings to use, and can I change them? I just got my first proper AirPrint printer (the Canon PIXMA 7120).

Like all printers, it has a ton of different settings for print quality, etc, and when you print from OSX, you get a print dialogue that lets you select things like 


Quality
Media type
Paper source
Etc.


But when printing from iOS native apps (I was using "Photos") the only choice I got was to select the AirPrint printer to print to.

When I printed, either iOS or the printer seems to have decided to use the tray that's dedicated to (4x6 or 5x7) photos, and to print in (high) photo quality, and spat out a beautiful print.

It seems possible that it makes assumptions based on the app you start from ("Photos" is probably sending a picture, while "Pages" more likely has a doc.

So, my questions is:

How does it decide what settings to use, and can I change them?

I might want it to print an 8X10 photo, or a pages doc on photo paper, etc.
The app ("Photos" in this case) makes those decisions based on your content and on what your printer supports.

If you are uncomfortable with this I have developed an app for printing photos that lets you control paper size, job type, sizes (inches or cm), crop, layout and ppi: http://www.clafou.com/print