jQuery(function(){
	jQuery(window).scroll(function(){
		var windowHeight =jQuery(window).height();
		var windowTop =jQuery(window).scrollTop();
		jQuery('.underz').each(function(){
			var objectImage =jQuery(this).offset().top;
			if(windowTop > objectImage - windowHeight*3/5){jQuery(this).css('background-size','100% 100%')};
		});
	});
});