I went outside for the first time to test the camera. Right now it's really winter and about -20 degrees Celsius (about -4 F). I zoomed in a tree at full zoom and shot for a while. When I now look at the clip - the picture kind of "waves", almost like a hot desert clip.

Is it breathing that I see?
Why/how is this "possible"?
Can it be avoided (except NOT zoom in to much or buy a new lens)?

I have the Canon HD KH19x6.7 lens (VCL-719BXS) on a F330.

Was there possibly a warm air current between you and the tree? Sound like hot air turbulence.

Haha... It might have been so!
I was actually standing on the balcony - with the door open. - "Big laugh!"

But anyway - what is breathing?

Breathing is the way the image gets smaller or larger as you turn the focus ring. Most lenses exhibit some breathing as you focus.

Alister:
Ahh - so that is the name of that "phenomenon" - and a quite annoying one!
Thanks, I did not know the english word for it, even that it now seem quite obvious :)