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Compared to... (contd.)

Colour Chart Comparison

Now we'll use the data in our review database to compare the C-40Z's colour and resolution to three other four megapixel digital cameras: the Canon PowerShot S40, Canon PowerShot G2 and Sony DSC-S85.

Colour charts are shot in daylight, Auto White Balance, EV compensation +0.3 (all cameras), measured light ~10 EV. This test is also dependent on the accuracy of the camera's auto white balance, the colour charts are shot in daylight but some camera's white balance is better than others. All cameras are given 20 seconds to "settle" before the shot is taken.

Olympus C-40Z Canon PowerShot S40
Canon PowerShot G2 Sony DSC-S85

It's amazing how close the C-40Z and S40 are for colour reproduction (apart from dark blues where the S40 does seem to cope better), both have good, vivid and accurate colour. The C-40Z puts away Olympus's history of undersaturated colour.

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

Patch Olympus
C-40Z
Canon
PowerShot S40
Canon
PowerShot G2
Sony
DSC-S85
Black 30,31,29 30,30,30 45,43,42 17,17,19
       
Middle Gray 100,99,99 103,102,103 107,106,110 76,81,79
       
White 214,216,211 215,210,211 208,210,208 188,189,189
       
Magenta 208,51,116 199,41,113 196,37,116 170,12,124
       
Red 196,45,41 196,33,42 195,30,35 176,0,40
       
Yellow 206,207,50 211,192,38 205,195,20 181,180,14
       
Green 8,143,63 33,140,67 43,152,68 24,131,27
       
Cyan 17,155,224 26,160,223 23,169,234 23,158,175
       
Blue 49,48,111 33,44,116 61,56,133 23,31,112
       


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 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.

Horizontal resolution Vertical resolution 5 degree diagonal res.
Olympus C-40Z
Canon PowerShot S40
Canon PowerShot G2
Sony DSC-S85

Measurable findings (three measurements taken for each camera):

Camera Measurement Absolute Res.  Extinction Res. 
Canon PowerShot S40 Horiz LPH 1250  *1400 
Vert LPH 1100  1400 
5o Diagonal LPH 1000  n/a 
Olympus C-40Z Horiz LPH *1200  *1350 
Vert LPH 1100  1400 
5o Diagonal LPH 1000  n/a 
Canon PowerShot G2 Horiz LPH 1250  *1450 
Vert LPH 1200  *1500 
5o Diagonal LPH 1000  n/a 
Sony DSC-S85 Horiz LPH 1250  *1650 
Vert LPH 1200  1650 
5o Diagonal LPH 1000  n/a 

* Some artifacts / moiré visible

Definition of terms:

LPH Lines per Picture Height (to allow for different aspect ratios the measurement is the same for horizontal and vertical)
5o Diagonal Lines set at 5o 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.

The C-40Z puts up a good fight, producing a good 1200 lines/picture height horizontally and 1100 lines/picture height vertically. This is virtually identical to Canon's S40 (but not quite, the C-40Z's lens being a little softer). It's a shame about the strong moire pattern and white halo sharpening artifact.

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