The ideal nature background

Out of focus foliage backgrounds should ideally be so out of focus that there is virtually no detail.  That forces all of the attention on the subject -- in this case a glass frog that I photographed in Costa Rica.  While this is a captive frog, my photo tour group and I took it outside and situated it such that the trees behind it were far enough away so that with any lens and any lens aperture, they would remain completely blurred.  My lens aperture here was f/11, and still the vegetation is completely undefined.  My other settings were 1/6 of a second (risky when photographing animals, but this little frog was perfectly still and I was using a tripod) and 400 ISO.  I used a 70-200m f/2.8 lens set to 135mm.