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Resolution Chart Comparison

Shots here are of the PIMA/ISO 12233 standard resolution test chart (more of which are available in our comparison database). This resolution chart allows us to measure the actual performance of the lens and sensor system. It measures the ability of the camera to resolve lines at gradually higher resolutions and enables us to provide a definitive value for comparison purposes. Values on the chart are 1/100th lines per picture height. So a value of 15 equates to 1500 lines per picture height.

Studio light, cameras set to auto, all settings factory default. Aperture selected for optimum sharpness. Exposure compensation +0.7 EV to +1.3 EV. Sigma SD10 & SD9 image produced with default parameters in Photo Pro.

Sigma SD10 Canon EOS 10D
Nikon D100 Sigma SD9

Sigma SD10 Canon EOS 10D
Nikon D100 Sigma SD9

Sigma SD10 Canon EOS 10D
Nikon D100 Sigma SD9

Sigma SD10 Canon EOS 10D
Nikon D100 Sigma SD9

Sigma SD10 Canon EOS 10D
Nikon D100 Sigma SD9

Measurable findings (three measurements taken for each camera):

Camera Measurement Absolute
Res.
Extinction
Res.
Sigma SD10 Horiz LPH 1550  >2000 
Vert LPH 1550  >2000 
5° Diagonal LPH 1000  n/a 
Canon EOS 10D Horiz LPH 1600  1900 
Vert LPH 1450  1850 
5° Diagonal LPH + 1000  n/a 
Nikon D100 Horiz LPH 1600  * 1850 
Vert LPH 1300  * 1700 
5° Diagonal LPH + 1000  n/a 
Sigma SD9 Horiz LPH 1550  >2000 
Vert LPH 1550  >2000 
5° Diagonal LPH 1000  n/a 

* Moiré is visible, + Chart maximum

Definition of terms:

LPH Lines per Picture Height (to allow for different aspect ratios the measurement is the same for horizontal and vertical)
5° Diagonal Lines set at 5° diagonal
Absolute Resolution Still defined detail (below Nyquist frequency*)
Extinction Resolution Detail beyond camera's definition (becomes a solid gray alias)
n/a Not Available (above the capability of the test chart)
n/v Not Visible (not visible on test results)

* Nyquist frequency defined as the highest spatial frequency where the sensor can still
faithfully record image detail. Beyond the Nyquist frequency aliasing occurs.

As we expected identical results to the SD9, and with good reason considering the design of the sensor and the fact that the pixel count hasn't changed. That's to a lack of a color filter the X3 sensor doesn't suffer from color moire at the limits of resolution.

Because the X3 sensor doesn't employ an anti-alias (low pass / blur) filter it continues to deliver detail past Nyquist. Taking the vertical resolution bar as an example we can count all nine lines up to our 'absolute resolution' measurement of around 1550 LPH, after this point lines begin to merge and by 2000 LPH we can count five obviously combined lines. In a real image this could be the detail of leaves on a distant tree or bricks on a distant wall. At the time of my SD9 review there was much debate over the 'validity' of this extra detail. My opinion on this matter is that this detail is at least of photographic merit, it is the correct color and represents detail that the human eye although not able to distinguish perfectly would also see as a broken texture, it's certainly better than the blurred area we would get from the anti-alias filter of a Bayer sensor camera.

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