Display different image size using ACF
//To display an image using ACF, one would set the image custom field to image url and call the img as follows:
<?php if( get_field( 'field_name' ) ): ?>
<?php while( has_sub_field( 'field_name' ) ): ?>
<img src="<?php the_sub_field( 'image' ); ?>" alt="">
<?php endwhile; ?>
<?php endif; ?>
// To display a different size, ie. thumbnail, medium, large or custom size you can use the following:
<?php if( get_field( 'field_name' ) ): ?>
<?php while( has_sub_field( 'field_name' ) ): ?>
<?php $image = wp_get_attachment_image_src( get_sub_field( 'image' ), 'image_size' ); ?> //change this to whatever size you want
<img src="<?php echo esc_url( $image[0] ); ?>" alt=""> // Make use you have images set to image ID in the ACF option
<?php endwhile; ?>
<?php endif; ?>