Compared to... (contd.)

Colour Chart Comparison

We'll now compare the G2's colour reproduction and resolution to the Olympus C-4040Z, Sony DSC-S85 and Nikon Coolpix 995 (the only three megapixel digital camera here, so it won't be included in the resolution 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 G2 Olympus C-4040Z
Sony DSC-S85 Nikon Coolpix 995
How far we've come, four cameras from four different manufacturers all delivering quite similar colour reproduction. There isn't a single colour patch here that's noticeably 'worse' than the next, each camera has its own slightly different characteristics but overall they're very close. The G2 shows its preferences for light blue as well as fairly strong red and yellow.

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 G2		 Olympus
C-4040Z 		Sony
DSC-S85

Nikon
Coolpix 995
Black 45,43,42 35,36,35 17,17,19 25,25,23
       
Middle Gray 107,106,110 111,105,110 76,81,79 103,103,102
       
White 208,210,208 211,210,217 188,189,189 215,215,211
       
Magenta 196,37,116 190,46,110 170,12,124 207,38,117
       
Red 195,30,35 178,44,45 176,0,40 197,31,50
       
Yellow 205,195,20 191,195,65 181,180,14 216,188,36
       
Green 43,152,68 41,145,84 24,131,27 8,136,61
       
Cyan 23,169,234 52,166,220 23,158,175 52,164,196
       
Blue 61,56,133 75,58,118 23,31,112 41,33,84
       

Again, although there's definitely some difference in the amount of saturation there's not a huge difference between these four cameras, maybe the DSC-S85 gets the edge for slightly 'purer' primary colours. But it really is a matter of personal preference. The G2 and the Coolpix 995 both allow the user to change the colour saturation output of the camera, thus allowing you to decide on your preferred output.

Red Channel Noise

Something we noticed early on with the current crop of 3 megapixel cameras was a certain amount of noise in the red channel. This was most visible in the light blue of skies or painted walls. Our colour patch test chart turned out to be a good "leveller" and a way to measure the performance of one camera to the next.

The samples below are of 40 x 40 blocks cropped from the colour comparison charts above of the Blue and Cyan patches. Each block is then broken down into it's red green and blue channels and reflected as such directly below.

While the G2 isn't entire devoid of red channel noise it does seem to at least have it under control, again the best performer in this comparison appears to be the Sony DSC-S85.

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.
Canon PowerShot G2
Olympus C-4040Z
Sony DSC-S85

Measurable findings (three measurements taken for each camera):

Camera Measurement Absolute Res.  Extinction Res. 
Canon PowerShot G2 Horiz LPH 1250  *1450 
Vert LPH 1200  *1500 
5o Diagonal LPH 1000  n/a 
Olympus C-4040Z Horiz LPH 1150  *1350 
Vert LPH 1100  1400 
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 G2 is up there with the DSC-S85 for absolute resolution, approximately 1200 lines/picture height in both horizontal and vertical directions is what we'd expect of a four megapixel digital cameras. What's slightly disappointing are the jagged 'stepping' edges to the G2's diagonals and the odd misplaced pixels once resolution goes beyond the camera's ability.

I would suggest that these strong jaggies are a sharpening artifact, clearly they really shouldn't be there.