Canon 20Da has a
8.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor . On the other hand, Canon 70D has a
20.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor and features Digic 5+ processor.
Canon 70D's sensor provides 12MP more than Canon 20Da'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 20Da and 70D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 20Da and Canon 70D Cameras
Canon 20Da and Canon 70D 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. On the other hand, since Canon 20Da has 143% larger pixel area compared to Canon 70D, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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
Canon 20Da
or the
Canon 70D ,
including hyperfocal distance.
