By using the ID, you can specify which crop size of the image and even get the name of the file!
NOTE: select ID option when creating custom field.
<?php
$image = wp_get_attachment_image_src(get_field('image_test'), 'full');
echo '<img src="'.$image[0].'" alt="'.get_the_title(get_field('image_test')).'" />';
?>
