Both Canon 77D and Pentax K-3 have 24.0 MP resolution sensors but Canon 77D's sensor is APS-C (22.3 x 14.9 mm ) and Pentax K-3's sensor is APS-C (23.5 x 15.6 mm ).
Since Pentax K-3's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Canon 77D.
One other difference between these two cameras that is worth mentioning is that Pentax K-3's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the 77D and K-3 sensor size comparison.
As seen above, Pentax K-3 has a 1.1x Larger sensor area than Canon 77D. 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.
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 77D and Pentax K-3 sensors have been tested by DxO and the results show that K-3 has a better overall score of 80, 2 points higher compared to 77D's score of 78.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Canon 77D |
78 |
23.6 bits |
13.3 Evs |
971 ISO |
Pentax K-3 |
80 |
23.7 bits |
13.4 Evs |
1216 ISO |