Pentax K-7 has a
15.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor and features Prime II processor. On the other hand, Canon 550D has a
18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Digic 4 processor.
Below you can see the K-7 and 550D sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-7 and Canon 550D Cameras
Pentax K-7 and Canon 550D 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. Pentax K-7 and Canon 550D sensors have been tested by DxO and the results show that 550D has a better overall score of 66, 5 points higher compared to K-7's score of 61.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K-7
61
22.6 bits
10.6 Evs
536 ISO
Canon 550D
66
22.0 bits
11.6 Evs
807 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
Pentax K-7
or the
Canon 550D ,
including hyperfocal distance.
