So for the acf/render_field documentation, it says to target a specific field, you only have to add the type of the file after the basic filter name. However, in acf-field.php, the correct syntax is acf/render_field/type={$field['type']}. For an image field, this would look like acf/render_field/type=image.
Pulled my hair out for ten minutes trying to figure it out until I decided to look at the code.
Hope this helps!
http://www.advancedcustomfields.com/resources/acf-render_field/
I can also confirm having pulled hair due to this. Please update the documentation for render_field!
Hair pulled report here too.
The docs are still not fixed.
