i have JVC-HD110 camera WHY MY focus changes when i move the camera i mean when i zoom and focus and then i move the camera to something different .
the focus go out of focus any help thanks .

a pro type lens needs to be re-focused when moving from 1 subject to another that is nearer or farther away than the original subject that was focused on. obviously there is no auto focus (that's worth using) on a pro lense. however it COULD be the backfocus is out

You must set your backfocus to get
the correct flangeback, on the other side
some user switch on the makrofunction of
the lens.

The result due to the focus is the same like
a wrong flangeback.

my back focus is ok i know when my back focus is out so it is not the back foucs ?

what do you mean by switch on the makrofunction ?

When you use for minimum object-distances
the macro on your lens (on Fujinon you must
switch a little plastic switch - on Canon-lenses you
push and change in the macroarea of the lens),
sometimes that will be forgotten when its
only 1 mm on the macro.

Then it looks like a incorrect flangeback (backfocus).

i have JVC-HD110 camera WHY MY focus changes when i move the camera i mean when i zoom and focus and then i move the camera to something different .
the focus go out of focus any help thanks .

Tamim - don't know if this is a communication problem but you do realise the camera doesn't autofocus? When you move the camera on to a different object at a different focal length from the lens of course you have to re-focus... that's expected.

If you are referring to zoom in and focus and zoom out,the object you originally focussed on should remain in focus IF the backfocus is set correctly. The only exception would be if you had your iris stopped down too far (anything much above F5 for 1/3" chips, F8 OK at a pinch) - nothing will ever focus correctly then. It may "appear" to be in focus when zoomed in but it is not -it just becomes more apparent on wider shots.