Supertele choices

[neuroanatomist]

Correct, Rich, except that contrast detect isn't less accurate than phase detect (it's as accurate or better, since focusing is done directly using the image sensor). It's just a lot slower...

[ahab1372]

Correct, Rich, except that contrast detect isn't less accurate than phase detect (it's as accurate or better, since focusing is done directly using the image sensor). It's just a lot slower...

Roger at Lensrentals has published a series of articles around AF, the first one compares Phase vs Contrast vs Manual:
http://www.lensrentals.com/blog/2012...-shot-accuracy

Interesting read, part 2 and 3a and 3b compare different lenses on different bodies

Arnt

[Richard Lane]

Heres a link that shows the different amount of cross-type AF sensor points with regards to the selected lens and/or extender: (Pg.36-39)

Group A to Group G:


http://cpn.canon-europe.com/files/education/technical/eos_1d_x_explained/AF_guide_EOS-1DX_eng.pdf

If someone thinks they need 500mm most of the time then they will be able to use 41 cross-type points, but with the 1.4X, that number will drop to 21, or essentially in half to Group E.

The 600mm f/4 will maintain the 41 cross-type points, Group C.

Naturally, the bare 70-200mm f/2.8L IS, 300mm f/2.8L IS and 400mm f/2.8L IS will also benefit from the dual cross-type points or Group A.

Incidentally, I thought it was interesting that the new 24-70mm f/2.8L II is group A, while the older 24-70mm f/2.8L was in Group B.

Other notable differences were that the 800mm f/5.6 can use 21 cross-type points, but it can only choose between 47 points, whereas the 600mm + 1.4X @ 840mm can also use 21 cross-type points, however all 61 AF points are available for selection.

Rich