Originally Posted by Chewy734
Oops. I meant the 100-400mm f/4.5-5.6L IS.
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?
don't forget it would be 640mm on a crop body.... sort of
it's a lot of zoom on a crop body. You will never really need any more then that unless you do 2-3 trecks into the woods a week like Dave does.