Canon EF400mm f/4 DO IS II USM Instructions Manual page 22

17. Extension Tubes
(Sold Separately)
You can attach extension tube EF12 II or EF25
II for magnified shots. The shooting distance and
magnification are shown below.
Focusing Distance Range (mm)
Close distance Long distance Close distance Long distance
EF12 II 2753 13407
EF25 II 2362
MF mode is recommended for accurate focusing.
Magnification (×)
0.17
6638 0.22
0.03
0.07
ENG-21