Display relevant contents if radio button is clicked using knockout.js
Not sure how much better it is, but some would say it could look nicer to intialize everything to false, then only change when true.  Like so:

self.print_size_radio.subscribe(function(p) {

   self.print_size_standard(false);
   self.print_size_13_19(false);
   self.print_size_contact(false);
   self.print_size_custom(false);

   if (p == 'Standard') {
      self.print_size_standard(true);
   } 
   else if (p == '13 x 19') {
      self.print_size_13_19(true);
   } 
   else if (p == 'Contact Sheet') {
      self.print_size_contact(true);
   } 
   else if (p == 'Custom Size') {
      self.print_size_custom(true);
   }
});