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Compared to... (contd.)

Colour Chart Comparison

Now we can compare the C-700UZ to a couple of other cameras, using samples from our test archives we will now compare its image quality (colour and resolution) to the Canon PowerShot A20, Sony MVC-CD200 and Nikon Coolpix 950.

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-700UZ Canon PowerShot A20
Sony MVC-CD200 Nikon Coolpix 950

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-700 UZ
PowerShot A20
Coolpix 950
Black 21,25,25 16,17,17 28,24,27 20,20,20
Middle Gray 94,104,109 88,91,90 86,98,102 105,108,108
White 194,204,210 204,206,203 184,198,196 198,198,198
Magenta 173,50,115 194,33,98 196,17,118 208,44,122
Red 173,24,24 189,22,29 192,7,23 215,31,41
Yellow 179,180,14 199,185,25 180,189,22 203,185,77
Green 32,130,51 18,125,59 0,164,37 0,148,67
Cyan 43,174,225 26,146,200 0,186,189 39,170,204
Blue 33,51,130 23,27,86 57,31,148 57,51,132

The C-700 UZ does well, overall colours are good, an even balance across the board. As we spotted on the previous page greens have a slight yellow taint (though no more in % terms than other digital's).

Red Channel Noise

Something we've commented on previously is noise in the red colour channel in what should be pure blues. 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.

Blues are definitely better (more saturated) than the Canon A20, however they do seem to contain a fair amount of noise in the red channel.

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.

Olympus C-700 UZ
Canon PowerShot A20
Sony MVC-CD200
Nikon Coolpix 950

Measurable findings (three measurements taken for each camera):

Camera Measurement Absolute Res. Extinction Res.
Olympus C-700 UZ Horiz LPH * 800 1000
Vert LPH * 800 1050
Diagonal LPH * 700 900
Canon PowerShot A20 Horiz LPH * 820 1000
Vert LPH 800 1050
Diagonal LPH 800 900
Sony MVC-CD200 Horiz LPH * 850 1050
Vert LPH 850 1050
Diagonal LPH 800 900
Nikon Coolpix 950 Horiz LPH 750 1050
Vert LPH 750 1050
Diagonal LPH 800 n/a

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 moiré effect on the C-700 UZ resolution charts is probably the worse I've seen, not a performance I'd expect of a second generation 2 megapixel and certainly not in line with other (even lesser priced) 2 megapixels. Resolution is better than the two year old Coolpix 950 but less than the A20 and CD200, probably what we'd expect of a complex 10x optical zoom.

If you take a closer look at the resolution charts it's also worth noting that the lens exhibits a certain amount of softness in the corners.

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