Resolution Chart Comparison (JPEG)

Shots here are of our 'version two' resolution chart which provides for measurement of resolution up to 4000 LPH (Lines Per Picture Height). A value of 20 equates to 2000 lines per picture height. For each camera the relevant prime lens was used. The chart is shot at a full range of apertures and the sharpest image selected. Studio light, cameras set to aperture priority (optimum aperture selected), image parameters default. Exposure compensation set to deliver approximately 80% luminance of white area.

Sigma DP2 (2.3 MB, 4.69x3 MP) Olympus E-P1 (5.4 MB, 12.3 MP)
Ricoh GRD III (3.3 MB; 10.0 MP) Sony DSLR A330 (2.5 MB, 10.2 MP)

Sigma DP2 Olympus E-P1
Ricoh GRD III Sony DSLR A330

Sigma DP2 Olympus E-P1
Ricoh GRD III Sony DSLR A330

Sigma DP2 Olympus E-P1
Ricoh GRD III Sony DSLR A330

Measurable results

Camera Measurement
Sigma DP2 Horizontal LPH * 1500  * 2600 
Vertical LPH * 1400  * 2550 
Olympus E-P1 Horizontal LPH 2200  * 2750 
Vertical LPH 2250  * 2650 
Ricoh GR Digital III Horizontal LPH 1800  * 2200 
Vertical LPH 1900  * 2500 
Sony A330 Horizontal LPH 1900  2450 
Vertical LPH 1900  2450 

* Moiré is visible
+ Chart maximum
LPH Lines per Picture Height (to allow for different aspect ratios the measurement is the same for horizontal and vertical)
Absolute resolution Point at which all lines of a resolution bar are still visible and defined, beyond this resolution loss of detail occurs (below Nyquist frequency).
Extinction resolution Detail beyond camera's definition (becomes aliased)

Although its resolution figures are very impressive for a camera that puts out only 4.7 megapixel images, they just can't quite keep up with the higher-resolution conventional sensor cameras here. Part of this is down to the use of a mono test chart, which is fairly easily rendered by Bayer sensors - the Sigma's Foveon chip should be able to render transitions between colors more accurately (at the pixel level, at least). The effect was demonstrated in the DP1 review. However, the nominal resolutions (pixel counts) of the competitors have moved on since that point, which will make up for much of the difference.