This example shows how to display a custom size of the selected image when using the image array return type. This return type allows us to easily access extra image data such as sizes, width, height and more.

ACF_IMAGE

<?php 

$image = get_field('image');

if( !empty($image) ): 

	// vars
	$url = $image['url'];
	$title = $image['title'];
	$alt = $image['alt'];
	$caption = $image['caption'];

	// thumbnail
	$size = 'thumbnail';
	$thumb = $image['sizes'][ $size ];
	$width = $image['sizes'][ $size . '-width' ];
	$height = $image['sizes'][ $size . '-height' ];

	if( $caption ): ?>

		<div class="wp-caption">

	<?php endif; ?>

	<a href="<?php echo $url; ?>" title="<?php echo $title; ?>">

		<img src="<?php echo $thumb; ?>" alt="<?php echo $alt; ?>" width="<?php echo $width; ?>" height="<?php echo $height; ?>" />

	</a>

	<?php if( $caption ): ?>

			<p class="wp-caption-text"><?php echo $caption; ?></p>

		</div>

	<?php endif; ?>

<?php endif; ?>