Canon 400D has a
10.0MP APS-C (22.2 x 14.8 mm ) sized CMOS sensor . On the other hand, Canon T6s has a
24.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features DIGIC 6 processor.
Canon T6s's sensor provides 14MP more than Canon 400D'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 400D and T6s sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 400D and Canon T6s Cameras
Canon 400D and Canon T6s have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Canon 400D and Canon T6s sensors have been tested by DxO and the results show that T6s has a better overall score of 70, 8 points higher compared to 400D's score of 62.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 400D
62
22.1 bits
11.0 Evs
664 ISO
Canon T6s
70
22.6 bits
12.0 Evs
915 ISO
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 400D
or the
Canon T6s ,
including hyperfocal distance.