For light graffiti, you need a camera with manual controls and a very slow shutter speed.

Both cameras have the necessary manual control.

The slowest shutter speed is:

ZS5 - 60 seconds
HZ30W - 16 seconds

I would choose the ZS5 as it will give me more time to complete the graffiti.

For those who are not familiar with light graffiti, here is a link that will show you some examples:

http://www.toxel.com/inspiration/2009/01/08/20-beautiful-examples-of-light-graffiti/

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