This is how you read the code. You can see the silver and black at the film cartridge. So, it tells the camera what ISO is it, and how many frames does the film has.
|Credit to http://www.oocities.org/yosemite/2131/dx-code.html|
Why do so? Because ISO1600 is so expensive!!! which will cost RM35 per roll. I will test about it.