For ACF users, creates an easy to use function that wraps your image in HTML5 <figure> adds <figcaption>. Also adds Schema markup in JSON LD. Parameters are 1. ACF field name, 2. Size, 3. Figure CSS class, 4. Figcaption CSS class.

acf-seo-image.php

function fsc_figure( $image, $size, $imageclass, $captionclass ){

	/**
	* Let plugins pre-filter the image meta to be able to fix inconsistencies in the stored data.
	*
	* @param string 		$image    			The ACF field name (i.e. 'your_photo_name').
	* @param string  		$size    				Thumbnail size (i.e. 'Thumbnail', 'Medium', 'Large')
	* @param string 		$imageclass     The Figure class you want to use (ex: 'my-figure') 
	* @param string    	$captionclass 	The Figcaption class you want to use (ex: 'caption-blue') 
	*/

		$image = get_field( $image );
		$size = $size;
		$thumb = $image['sizes'][ $size ];

		if( !empty($image) ):  ?>

			<figure class="<?php echo $imageclass; ?>">
			
				<?php echo wp_get_attachment_image( $image['ID'], $size, false, array( 'alt' => $image['alt'] ) );  ?>

					<figcaption class="<?php echo $captionclass; ?>">

						<?php echo $image[ 'caption' ]; ?>

					</figcaption>

			</figure>

			<script type="application/ld+json">
				{
				"@context": "http://schema.org",
				"@type": "ImageObject",
				"author": "<?php the_author(); ?>",
				"contentUrl": "<?php echo $thumb; ?>",
				"datePublished": "<?php echo $image[ 'created_timestamp' ]; ?>",
				"description": "<?php echo $image[ 'alt' ]; ?>",
				"name": "<?php echo $image[ 'title' ]; ?>",
				"copyright": "<?php echo $image[ 'copyright' ]; ?>"
				}
			</script>

		<?php endif; 
}

Thanks to @kevinwhoffman for incorporating the WordPress responsive src set.