Both Nikon D70 and Pentax ist DL2 have APS-C sized 6.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the D70 and ist DL2 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D70 and Pentax ist DL2 Cameras
Nikon D70 and Pentax ist DL2 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. Nikon D70 and Pentax ist DL2 sensors have been tested by DxO and the results show that ist DL2 has a better overall score of 65, 15 points higher compared to D70's score of 50.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon D70
50
20.4 bits
10.3 Evs
529 ISO
Pentax ist DL2
65
22.9 bits
11.1 Evs
639 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
Nikon D70
or the
Pentax ist DL2 ,
including hyperfocal distance.
