Canon PowerShot G3 Review: 22. Compared to...: Digital Photography Review

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.


Canon PowerShot G3	Canon PowerShot G2

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 PowerShot G3	Canon PowerShot G2	Nikon Coolpix 4500	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 1/100^th 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.

Canon PowerShot G3

Canon PowerShot G2

Nikon Coolpix 4500

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.

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