It is always difficult to get good depth of field when photographing with telephoto lens. Especially when photographing subjects that are not very far away from you. It is visually disturbing to have foreground objects out of focus in the image.
I was photographing an iguana in Florida with my lens at 600mm. It was impossible to get both the iguana and the leaves on the tree in focus. At first I was so busy making sure I was getting the iguana’s eye in focus, I didn’t even notice the out of focus leaves. But when viewing the image on the LCD they were glaringly apparent. Watch the video to see how I solved the problem.