I got my DMC-ZS40 about a year ago. It's a direct descendent of the ZS20 that I had earlier, but with two important additions -- a 30X zoom lens and a real (though tiny) electronic viewfinder. All of this in a tiny camera, not much bigger than the DMC-LF1 that I'd been using. Seems too good to be true. And in a way, it was.
If the LF1 is a diamond, the ZS40 is a cubic zirconium. It's bigger and more impressive in some ways, but not so much in others. The ZS40 is what you get when you start with a ZS30 and push it to its limit. And it's my first Panasonic made in China rather than in Japan. The lens on the ZS40 has the longest zoom range of any camera I've owned, and it's very similar to the lens on the ZS30, but tweaked for additional range at the long end.
The biggest problem with the ZS40 is its insane, overcrowded 18 megapixel sensor. Too many pixels jammed into too small a space. No good will come of this. All those extra pixels take up too much space and, even worse, they slow things down when you move your images to the computer. Every sort of processing takes longer, and the larger image files take up more memory making it difficult to do things like panoramas.
I ended up setting the ZS40 to 12 megapixels. The quality looked about the same as when set to 18 megapixels, but things went a lot smoother.
Another problem was the ZS40's zoom lens. In designing a lens with this long a range, you have to make compromises. Most of the time, they won't have a great affect on the image quality.
There'll be some more on the ZS40 in part two of this article.
Some technical notes: All of the pictures were shot with my Panasonic DMC-ZS40. The post processing was done with LightZone-3.