Паралакс эффект

<section class="sect_2">
	<div class="header_text">
		Lorem ipsum
	</div>
	<img src="images/2.jpg" alt="alt">
</section>

section{
	height: 100vh;
	background-color: #666;
	position: relative;
	overflow: hidden;
}
.header_text{
	font-family: "Arial",sans-serif;
	text-transform: uppercase;
	color: #fff;	
	font-weight: bold;
	font-size: 40px;
	display: inline-block;
	widows: 240px;
	height: 40px;
	text-align: center;
	position: absolute;
	top: 50%;
	left: 50%;
	margin-left: -120px;
	margin-top: -20px;
	z-index: 5;
}
.sect_2 .header_text{
	top: 20%;
}
.sect_2 img{
	position: absolute;
	width: 100%;
	top: -370px;
}

$(window).scroll(function () {
	var st = $(this).scrollTop();
	// console.log(st);
	$('.sect_2 img').css({
		"transform" : "translate(0%, " +st/20+"%"

	})
});