old_contents: Photo = function (doc) {
    _.extend(this, doc);
  };
  
  _.extend(Photo.prototype, {
  	getImgTag: function (dimension) {
  		return {
  			'class': 'lazy',
  			'data-src': _.str.sprintf(
  				'%s/photos/%s/%s',
  				Meteor.settings.public.uri.cdn,
  				dimension,
  				this.filename
  			),
  			'data-src-retina': _.str.sprintf(
  				'%s/photos/%s@2x/%s',
  				Meteor.settings.public.uri.cdn,
  				dimension,
  				this.filename
  			),
  			alt: this.title,
  			width: dimension,
  			height: dimension
  		};
  	}
  });
  
  Photos = new Mongo.Collection('Photos', {
  	transform: function (doc) { return new Photo(doc); }
  });
  
new_contents: Photo = function (doc) {
    _.extend(this, doc);
  };
  
  _.extend(Photo.prototype, {
  	getImgTag: function (dimension) {
  		return {
  			'class': 'lazy',
  			'src': 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7',
  			'data-src': _.str.sprintf(
  				'%s/photos/%s/%s',
  				Meteor.settings.public.uri.cdn,
  				dimension,
  				this.filename
  			),
  			'data-src-retina': _.str.sprintf(
  				'%s/photos/%s@2x/%s',
  				Meteor.settings.public.uri.cdn,
  				dimension,
  				this.filename
  			),
  			alt: this.title,
  			width: dimension,
  			height: dimension
  		};
  	}
  });
  
  Photos = new Mongo.Collection('Photos', {
  	transform: function (doc) { return new Photo(doc); }
  });
  
subject: Use a transparent pixel to hold the height