Some math questions from you guys

[MohaimenK]

70-200 2.8L would be 112-320mm if I was to use it with my T1i which gives me 120mm zoom over my 5dMK2. But if I was to get the 2x TC would that simply make it up to a 640MM at f5.6 (constant)??

My math says yes and hoping the camera works the same way.

 

[SensePhoto]

would also like to know the answer to this

 

[KmH]

Your math is correct.

Auto focus may have difficulty with an effective max aperture of f/5.6. A 2x TC can also have a negative effect on overall image quality.

 

[BuS_RiDeR]

Edit... Misread. Sorry you are correct.

 

[Overread]

The image quaility will take a noticable hit - however whilst the original 70-200mm f2.8 IS L took what most considered to be too much of a hit with the 2*TC the 70-200mm f2.8 IS L M2 takes a far smaller hit and its image quailty with the 2*TC is comparable to the 100-400mm L (from tests I've seen the 100-400mm has a very slight edge, but its so slight that you can't tell them apart - esp from a print or websize shot).

Eg: Original lens with 2*TC
little birds photos test - a set on Flickr

New M2 lens with the same 2*TC (M2 version of course)
Minsmere - a set on Flickr

In my experience I used the original with the 2*TC a about 2 or 3 times in total - whilst the M2 I'm quite happy to let the 2*TC sit on the lens as long as I need the range without any image quality worries.



PS - please note however that if shooting wildlife the animals will take into consideration your longer focal length and thus move that much further away from you - many think that they've a contract with canon to keep doing this until you get a 600mm or 800mm L lens

 

[D-B-J]

Your math is correct, but as others said, the image quality will be reduced probably more than you'd like.

 

[MohaimenK]

Thanks guys, I was looking at the new 2X TC III
I guess if it's too much then I can always pull out the 5d2 and shoot at 400MM which I believe I posted looks VERY good. (below). Granted this was shot through the dirty store glass window which is tinted.

Shot at f5.6 at 400mm with the 70-200 2.8II M2 with the 2x III TC