[putto]

1.4X / 2X 加左上去部機有咩影響
除左可以 1.4 / 2X 之外

如果我果部係550D

係咪本身部機既1.6 X 1.4或者2 再加埋支鏡丫...
咁如果係...仲有咩影響

[talestar]

YEs
if 70-200 f/4 + 1.4x for tele side = 200 x 1.6 x 1.4 = 448 mm
except for 1D series canon camera all aperture after f/5.6 do not have auto focus.
therefore all f/4 lens only can use 1.4x ( f/4 > f/5.6) still have AF
f/2.8 lens + 2x also have AF(f/2.8 > f/5.6)
1.4x add 1 stop of aperture
2x add 2 stop of aperture
But it still have MF