Compared to... (contd.)
Now we'll compare the Canon PowerShot G3 to a few other four megapixel digital cameras from our test archives. Here we're comparing colour and resolution to the previous Canon PowerShot G2, Nikon Coolpix 4500 and Sony DSC-S85.
Colour Chart Comparison
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 G3 | Canon PowerShot G2 |
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| Nikon Coolpix 4500 | 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 |
Canon PowerShot G2 |
Nikon |
Sony DSC-S85 |
| Black | 34,34,34 | 45,43,42 | 25,27,27 | 17,17,19 |
| Middle Gray | 102,105,105 | 107,106,110 | 101,100,102 | 76,81,79 |
| White | 212,212,212 | 208,210,208 | 211,210,209 | 188,189,189 |
| Magenta | 208,45,115 | 196,37,116 | 203,38,118 | 170,12,124 |
| Red | 203,34,44 | 195,30,35 | 189,22,43 | 176,0,40 |
| Yellow | 208,192,30 | 205,195,20 | 193,183,27 | 181,180,14 |
| Green | 23,138,73 | 43,152,68 | 29,140,61 | 24,131,27 |
| Cyan | 5,152,218 | 23,169,234 | 60,167,205 | 23,158,175 |
| Blue | 37,49,122 | 61,56,133 | 54,47,112 | 23,31,112 |
In the majority of cases the G3's response is quite similar to the G2 (no surprises really), however it is worth noting that the G3's black is darker (which will add a little more contrast to images) and that blues seem to have more purity (lower green / red levels). The G3's automatic white balance is very impressive with very clean pure greys and whites.
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).
| Horizontal resolution | Vertical resolution | 5 degree diagonal res. |
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| Canon PowerShot G3 | ||
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| Canon PowerShot G2 | ||
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| Nikon Coolpix 4500 | ||
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| Sony DSC-S85 | ||
Measurable findings (three measurements taken for each camera)
| Camera | Measurement | Absolute Res. | Extinction Res. |
| Canon PowerShot G3 | Horiz LPH | 1250 | 1400 |
| Vert LPH | 1200 | 1400 | |
| 5° Diagonal LPH | # 1000 | n/a | |
| Canon PowerShot G2 | Horiz LPH | 1250 | * 1450 |
| Vert LPH | 1200 | * 1500 | |
| 5° Diagonal LPH | # 1000 | n/a | |
| Nikon Coolpix 4500 | Horiz LPH | * 1200 | * 1350 |
| Vert LPH | 1100 | 1300 | |
| 5° Diagonal LPH | 1000 | n/a | |
| Sony DSC-S85 | Horiz LPH | 1250 | * 1650 |
| Vert LPH | 1200 | 1650 | |
| 5° Diagonal LPH | 1000 | n/a |
* Moiré is visible, # Jagged edges to 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.
As expected the G3 put in pretty much the same resolution performance as the G2, it appears as though Canon has decided to compromise extinction resolution (only slightly) for reduced moiré, this is probably a wise move. Compared to other four megapixel digital cameras the G3 has very good resolution, up there with the best (Sony's DSC-S85). It may be worth noting that Canon's sharpening algorithms appear to be accentuating the visibility of 'jaggies' on the 5° lines.
