Canon EF100-400mm f/4.5-5.6L IS II USM Lens Instructions For Use Manual page 17

11. Extenders (Sold Separately)
Lens specifications when using extender EF1.4x II/III or EF2x II/III are as follows.
Focal length (mm)
Aperture
Diagonal
Vertical
Angle of view
Horizontal
Maximum magnification (x)
Extender EF1.4x II/III
WIDE TELE
140
f/6.3-45 f/8-57
17° 35' 4° 25'
9° 50' 2° 25'
14° 40' 3° 40'
0.17 0.44
WIDE
560 200
f/9-64
12° 00'
7° 00'
10° 00'
0.26
Extender EF2x II/III
TELE
800
f/11-81
3° 05'
1°40'
2°35'
0.64
ENG-16