Hi,
This feels like a stupid question to be asking but its bugged me for a while!

Using a DOF calculator like this one:
Online Depth of Field Calculator (http://www.dofmaster.com/dofjs.html)

When it asks for focal length do I put in the real focal lens of the Z5 lens or the 35mm equivalent? 82mm or 590mm for max zoom on the Z5.

Thanks!

I too have had the same question.
The calculations seem to make sense if you enter:
4.1 for the focal length (mm) when the lens is wide and
82 when the lens is at max zoom.
Both numbers are found in the manual under specifications.

And don't forget to enter 1/3 inch sensor in the field above; Camera, film format or circle of confusion.