I think you would be better off returning a JSON object that contains just the data you need to serialize, not the whole class. Then your loadFromJson method would be a little easier to implement, and you wont be sending unnecessary data over the network. Example toJson():
toJson: function() {
return JSON.stringify({
photos: this.photos,
someImportantProp: this.someImportantProp,
anotherProp: this.anotherProp
});
}