Both Canon 1Ds MIII and Canon 5D MII have Full frame sized 21.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the 1Ds MIII and 5D MII sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 1Ds MIII and Canon 5D MII Cameras
Canon 1Ds MIII and Canon 5D MII 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.
DxOMark Sensor Scores
Both Canon 1Ds MIII and Canon 5D MII sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, 1Ds MIII has scored 80, 1 points higher than 5D MII.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 1Ds MIII
80
24.0 bits
12.0 Evs
1663 ISO
Canon 5D MII
79
23.7 bits
11.9 Evs
1815 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 1Ds MIII
or the
Canon 5D MII ,
including hyperfocal distance.
