Function to convert ACF image field into image tag with srcset.

the_field_srcset.php

<?php
/* 
	Usage: the_field_srcset('field_name');
	ACF field should return Image ID.
*/
function the_field_srcset($field, $before='', $after='', $size = 'full', $echo = true) {
	
	if (get_field($field)) {
		$img = wp_get_attachment_image(get_field($field), $size);
		
		
		if ($before) {
			$img = $before.$img;
		}
		
		if ($after) {
			$img = $img.$after;
		}
		
		if (!$echo) {
			return $img;
		}
		
		echo $img;
	}
}
?>