Panasonic ZS99 has a
20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine processor. On the other hand, Canon SX510 HS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Digic 4 processor.
Panasonic ZS99's sensor provides 8MP more than Canon SX510 HS'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 ZS99 and SX510 HS sensor size comparison.
Sensor Size and Resolution Comparison image of Panasonic ZS99 and Canon SX510 HS Cameras
Panasonic ZS99 and Canon SX510 HS have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Panasonic ZS99
or the
Canon SX510 HS ,
including hyperfocal distance.