An example of a shallow depth of field with long actual focal lengths (560 mm in this case, with effective focal length of ca. 900 mm). Notice that this picture is shot with rather small apreture, f-number being 10. Still the DOF is extremely thin.
Thermos (<a href="//commons.wikimedia.org/wiki/User:Thermos" title="User:Thermos">Thermos</a>)
<span class="int-own-work" lang="en">Own work</span>