Resolution Chart Comparison

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 DP1 (2,152 KB, 4.7 MP) Nikon D60 (2,665 KB; 10.2 MP)
Nikon D60 (downscaled) (1,050 KB; 4.7 MP) Ricoh GR Digital II (3,364 KB; 10 MP)

Sigma DP1 Nikon D60
Nikon D60 (downscaled) Ricoh GR Digital II

Sigma DP1 Nikon D60
Nikon D60 (downscaled) Ricoh GR Digital II

Sigma DP1 Nikon D60
Nikon D60 (downscaled) Ricoh GR Digital II

Measurable results

Camera Measurement
Sigma DP1 Horizontal LPH 1525  2400 
Vertical LPH 1500  2300 
Nikon D60 Horizontal LPH 2200  2300 
Vertical LPH 1800  2300 
Nikon D60 (downscaled) Horizontal LPH 1425  1850 
Vertical LPH 1250  1850 
Ricoh GR Digital II Horizontal LPH 1550  1825 
Vertical LPH 1525  1800 

* Moire 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)

The Sigma DP1 delivers an admirable resolution considering the size of its image output of not even five megapixels. While it outresolves the downscaled Nikon D60 image and almost matches the resolution of the ten megapixel Ricoh, it cannot really compete with a modern 10 megapixel DSLR such as the Nikon D60.

Remarkably in terms of extinction resolution (below Nyquist) it even narrowly beats the D60. The DP1 continues to deliver detail past Nyquist because the X3 sensor doesn't employ an anti-alias (low pass / blur) filter. Some will argue this is not 'real' detail (it is produced beyond Nyquist) but in any case it is useful as it improves the appearance of 'texture'. A Bayer sensor camera would simply capture a blurred area without any detail.