Casio's official blurb for the Z19 calls it "high performance", and claims that it has a 1.4-second start-up time and 0.008 sec shutter lag, although it is careful to qualify these statements. It can start up in 1.4 seconds if the monitor is switched off, and that fast shutter lag is only after it has already focused. Back here in the real world, the normal start-up time is approximately 2.3 seconds, which is still far from terrible, and the autofocus system is also nice and quick. It is also very reliable in most lighting conditions, although it does have a low-light limit. The Z19 has no AF assist lamp, so full darkness defeats it.
Shot-to-shot time in single-shot mode is approximately three seconds, which is actually a little on the slow side by recent standards, however in continuous shooting mode it can manage just over one frame per second, which isn't too bad. It's actually slightly faster for the first half-dozen frames, managing 1.4fps, but then the buffer fills up and it slows down.
Image quality is also reasonably good for what is after all quite a cheap camera. The lens produces some barrel distortion at wide angle, but centre sharpness is very good and the corners of the frame are also acceptably sharp. The 9.1MP sensor records a good level of detail, and the low compression in Fine quality mode produces image files of around 5.5MB with few if any JPEG artefacts. Colour reproduction is excellent, however the exposure metering does not cope especially well with strong backlighting, necessitating the use of exposure compensation in some situations. Dynamic range could also be better, with burned-out highlights and poor shadow detail in very high contrast conditions.
Image noise is about average for a camera in this class, with good results at 64 ISO, but progressively more noise as the ISO setting is increased. However the noise is quite well handled, and even at 800 ISO colour balance and contrast are maintained and images would make acceptable small prints, although results at the maximum 1600 ISO are a bit blotchy.
Although its specification is rather primitive by recent standards, and it is distinctly lacking in advanced features, the Casio Exilim EX-Z19 offers decent design and build quality, reasonably good performance and acceptable image quality for an attractively low price. However for just a little more money one can buy a similarly-sized camera offering many more features.