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      07-12-2011, 07:19 PM   #40
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Drives: 2006 BMW 330i ZPP, ZSP
Join Date: Dec 2008
Location: Minneapolis, MN

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Originally Posted by UdubBadger View Post
oh nice, how much?

wait... they make a 100-400 F4 IS? or did you mean the 70-200?
Oops. I meant the 100-400mm f/4.5-5.6L IS.

Originally Posted by UdubBadger View Post
Now that I think about it, if I do a 70-200 2.8 on my 40D (1.6x crop ratio) thats a 280mm equivalent still shooting @f/2.8. Then if I do a 1.4xTC I only lose 1 stop but my range goes up to 448mm and ends up being faster and longer than the f/2.8 losing 2 stops with the 2xTC @400mm.

Does that math make sense or am I not multiplying correctly?
The latter.

The 70-200 f/2.8 on my 40D gives you 200*1.6 = 320mm equivalent at f/2.8.
If you do the 1.4x TC, then on your 40D, you'll have 320*1.4 = 448mm equivalent at f/4.

If you use the 2x TC on your 5DM2 with that lens, you'll get 400mm at f/5.6.

Is that what you are trying to compare?

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