Difficult to say without more detail. Of the face of it, if it was a 'low energy' lamp (e.g. CFL or LED) and depending on quite where things were switched then capacitive coupling between the shower and lighting circuits might be another possibility.

Voltage drop (or rather the voltage rise on the N) might possibly account for it - there are strange switching systems around the world (e.g. 2-way systems  where each side of the lamp are independently switched between L & N rather simply opening or closing the circuit, and even split-phase systems where voltage drop on one side would pull the N voltage that way and so increase the apparent voltage seen by things on the other phase) - depends where the video has come from - such arrangements are rare this side of the Atlantic.

   - Andy.

I can say for sure it wasn't an led lamp from the look I would say it's an old style incandescent lamp. And was testing a ze of 0.45 ohms. 

From what your saying does that mean that when the voltage decreases on the line said it'll cause an increase on the neutral conductor? 

I can say for sure it wasn't an led lamp from the look I would say it's an old style incandescent lamp. And was testing a ze of 0.45 ohms. 

From what your saying does that mean that when the voltage decreases on the line said it'll cause an increase on the neutral conductor?