AG AF 100 lenses 14-140 lumix and 100-300 lumix zoom

[Eduardo Martinez]

I bought a camera panasonic AG AF 100 with two lenses 14 -140 lumix and 100-300 lumix . . When I make a zoom with focus and iris manual the lenses tray to correct the focus and make luminance´s variation . Is This something normal with the AG AF 100? Is this camera to be use only with primer lenses?

[ulisses]

Eduardo,

Any camera with any lenses that doesn't have a constant aperture will change the iris with the focal length. If you lens is 3.5-5.8, you have to set iris to 5.8 or more to avoid changes at any length. IF it is 3.5 at 14mm and 5.8 at 140mm, lets say your iris is set at 3.5, when you are at 140mm the iris must go to 5.8. There are lenses that keep the aperture (more expensive)
The focus in these lenses should change as well, because they are varifocal, video cameras have parfocal lenses, when focus doesn't change with zoom.

I hope this helps,
Ulisses