Hi Jonathan and thanks for your quick reply.
I have set the image field to ID. But after your reply I checked the code again and found the error.
I had used the_sub_field instead of get_sub_field.
So thanks for validating that your solution also worked on sub fields that pointed me in the right direction.
I saw your answer in this topic (http://support.advancedcustomfields.com/forums/topic/how-to-use-alt-tags/) and used the last solution you provided.
Final code that worked for me.
Code added to function.php
// Alt text for ACF get_sub_field images
function get_image_with_alt($imagefield, $postID, $imagesize = 'full'){
$imageID = get_sub_field($imagefield, $postID);
$image = wp_get_attachment_image_src( $imageID, $imagesize );
$alt_text = get_post_meta($imageID , '_wp_attachment_image_alt', true);
return '<img src="' . $image[0] . '" alt="' . $alt_text . '" />';
}
And then all it like this where you want the image in your template:
<?php echo get_image_with_alt('NAME OF THE IMAGE FIELD', get_the_ID(), ''); ?>
