Panasonic ZS1 has a 10.0MP 1/2.5-inch (5.744 x 4.308 mm ) sized CCD sensor . On the other hand, Canon 550D has a 18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Digic 4 processor.
Canon 550D's sensor provides 8MP more than Panasonic ZS1's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the ZS1 and 550D sensor size comparison.
![Panasonic ZS1 vs Canon 550D Sensor Size Comparison]()
Sensor Size and Resolution Comparison image of Panasonic ZS1 and Canon 550D Cameras
As seen above, Canon 550D has a 13.4x Larger sensor area than Panasonic ZS1. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.