is it true ???

[Daniel Browning]

i own one canon 40D and i was planning to buy the 100-400mm IS lens but one friend of mine told me that it might not work well together.

Your friend is wrong. They work very well together.

he said that this type of lens (big ones) works at it's full potential on higher quality bodies like 1D or similar ones.

He's wrong on this one too. The size of the lens (big vs small) doesn't enter into it.

can the small battery from my 40 D be to weak to "spin " this big lense?

No.


By the way, there is a certain relationship between contrast/resolution of images produces by EF lenses and sensor size, but it sounds like your friend isn't aware of it at all, so we wont go there.