Compared to... (contd.)
Colour Chart Comparison
Now we'll use the data in our review database to compare the S40's colour and resolution to three other four megapixel digital cameras: the Olympus C-40Z, 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.
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Canon PowerShot S40 | Olympus C-40Z |
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Canon PowerShot G2 | Sony DSC-S85 |
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 | Canon PowerShot S40 |
Olympus C-40Z |
Canon PowerShot G2 |
Sony DSC-S85 |
Black | 30,30,30 | 30,31,29 | 45,43,42 | 17,17,19 |
Middle Gray | 103,102,103 | 100,99,99 | 107,106,110 | 76,81,79 |
White | 215,210,211 | 214,216,211 | 208,210,208 | 188,189,189 |
Magenta | 199,41,113 | 208,51,116 | 196,37,116 | 170,12,124 |
Red | 196,33,42 | 196,45,41 | 195,30,35 | 176,0,40 |
Yellow | 211,192,38 | 206,207,50 | 205,195,20 | 181,180,14 |
Green | 33,140,67 | 8,143,63 | 43,152,68 | 24,131,27 |
Cyan | 26,160,223 | 17,155,224 | 23,169,234 | 23,158,175 |
Blue | 33,44,116 | 49,48,111 | 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. |
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Canon PowerShot S40 | ||
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Olympus C-40Z | ||
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Canon PowerShot G2 | ||
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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) |
image detail. Beyond the Nyquist frequency aliasing occurs.
The S40 did remarkably well, especially considering its tiny lens. Resolution was virtually identical to the G2, perhaps a little less in the vertical direction. Where the G2's lens will perform better is corner sharpness (the S40 can be a little soft in the corners) and its relative speed (F2.0 - F2.5 vs. F2.8 - F4.9). Also putting up a good fight is Olympus's C-40Z, although it's a shame about all that moiré.
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