Compared to... (contd.)

Here we will use our standard color and resolution charts to compare the Pentax Optio S to the Canon PowerShot SD100 (Digital IXUS II), Casio EXILIM EX-Z3 and Nikon Coolpix SQ. Note that both the Pentax Optio S and Casio EXILIM EX-Z3 needed +0.7 EV exposure compensation (compared to our normal +0.3 EV) to accurately expose our standard color chart comparison (below).

Color Chart Comparison

Color charts are shot in daylight, Auto White Balance, Canon & Nikon +0.3 EV compen. / Pentax & Casio +0.7 EV compen. This test is also reliant on the accuracy of the camera's auto white balance, the color charts are shot in daylight but some camera's white balance is better than others. All cameras are given 20 seconds for their white balance systems to settle before the shot is taken (often we will take up to eight shots and select the 'average' AWB result).

Casio EXILIM EX-Z3 Canon PowerShot SD100
Pentax Optio S Nikon Coolpix SQ

In the table below we're only measuring color. The RGB values were measured from a VGA reduced image (to average colors, remove noise and eliminate JPEG artifacts) using the Eyedropper tool in Photoshop with a 5 by 5 Average Sample Size.



PowerShot SD100

Optio S

Coolpix SQ
Black 26,26,27 24,26,25 23,24,26 39,40,40
Middle Gray 109,109,108 104,106,107 101,102,108 113,110,112
White 213,214,209 215,217,216 201,202,206 222,217,218
Magenta 218,70,109 217,48,118 186,21,99 219,49,122
Red 220,56,44 208,41,44 189,8,29 204,39,37
Yellow 221,201,68 210,203,29 214,194,62 195,206,63
Green 40,134,68 7,145,81 37,133,78 31,158,84
Cyan 22,167,188 15,159,228 25,148,196 74,170,235
Blue 42,42,98 43,48,113 42,38,103 49,56,137

The Casio's automatic white balance was accurate with virtually pure grays and whites. I was a little disappointed by the slightly muddy response to green, cyan and blue. We also saw this in our side-by-side comparison on the previous page, blues are far less saturated and light blues have too high a green level. There was also a far less distinct difference between Magenta and Red for the EX-Z3, compared to the other cameras.

Resolution 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 8 equates to 800 lines per picture height.

Studio light, cameras set to auto, all settings factory default. Exposure compensation +0.7 EV for all cameras (to compensate for the white background). Click on the camera name below the crops to download the full resolution chart (large JPEG's).

Horizontal resolution Vertical resolution 5 degree diagonal res.
Casio EXILIM EX-Z3 (1,589 KB)
Canon PowerShot SD100 (1,210 KB)
Pentax Optio S (1,754 KB)
Nikon Coolpix SQ (1,330 KB)

Measurable findings (three measurements taken for each camera)

Camera Measurement Absolute Res. Extinction Res.
Casio EXILIM EX-Z3 Horizontal LPH 1000  * 1250 
Vertical LPH 950  * 1200 
5° Diagonal LPH 900  n/a 
Canon PowerShot SD100 Horizontal LPH 1100  1300 
Vertical LPH 1000  * 1300 
5° Diagonal LPH # 900  n/a 
Pentax Optio S Horizontal LPH 1000  * 1250 
Vertical LPH 950  * 1200 
5° Diagonal LPH # 900  n/a 
Nikon Coolpix SQ Horizontal LPH 1100  * 1350 
Vertical LPH 1000  * 1350 
5° Diagonal LPH # 900  n/a 

* Moiré is visible, + Chart maximum, # Jagged diagonals

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 CCD can still faithfully record
image detail. Beyond the Nyquist frequency aliasing occurs.

Despite its good performance on the side-by-side studio comparison on the previous page the EX-Z3 produced an average resolution on our ISO standard test chart. It matched the Optio S (as we had expected) and was just lower than the PowerShot SD100. Still very respectable for an ultra-compact three megapixel digital camera.