Both Canon S120 and Canon 450D have 12.0 MP resolution sensors but Canon S120's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Canon 450D's sensor is APS-C (22.2 x 14.8 mm ).
Since Canon 450D'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 S120.
Below you can see the S120 and 450D sensor size comparison.
As seen above, Canon 450D has a 7.9x Larger sensor area than Canon S120. 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 S120 and Canon 450D sensors have been tested by DxO and the results show that 450D has a better overall score of 61, 5 points higher compared to S120's score of 56.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Canon S120 |
56 |
21.3 bits |
11.9 Evs |
246 ISO |
Canon 450D |
61 |
21.9 bits |
10.8 Evs |
692 ISO |