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Compared to... (contd.)

Colour Chart Comparison

Now we can compare the Digital IXUS v 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 S10, 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.

Canon Digital IXUS v (S110 Digital Elph) Canon PowerShot S10
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 Canon Digital
IXUS v
Canon
PowerShot S10
Sony
MVC-CD200
 
Nikon
Coolpix 950
Black 19,19,19 37,39,43 28,24,27 20,20,20
       
Middle Gray 92,104,111 112,111,128 86,98,102 105,108,108
       
White 194,206,213 209,213,220 184,198,196 198,198,198
       
Magenta 186,32,106 183,49,126 196,17,118 208,44,122
       
Red 181,26,30 173,40,54 192,7,23 215,31,41
       
Yellow 184,186,25 206,199,29 180,189,22 203,185,77
       
Green 13,123,61 58,137,96 0,164,37 0,148,67
       
Cyan 25,140,205 85,163,218 0,186,189 39,170,204
       
Blue 19,24,89 43,50,108 57,31,148 57,51,132
       

The IXUS v, no matter how many samples I took always left the image with a slight blue cast, this was the fault of the camera's auto white balance, and was a surprised compared to the results we got out of its bigger brother the IXUS 300. Otherwise colour balance was good, if a little pale in certain colours (blue).

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.

The IXUS v does well, almost no visible noise in the red channel and fairly good purity (if under saturated) for the blue patch. This is a good performance for an ultra-compact.

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, Exposure compensation +0.7 EV for all cameras.

Canon Digital IXUS v (S110 Digital Elph)
Canon PowerShot S10
Sony MVC-CD200
Nikon Coolpix 950

Measurable findings (three measurements taken for each camera):

Camera Measurement Absolute Res. Extinction Res.
Canon Digital IXUS v
(S110 Digital Elph)
Horiz LPH * 830 1000
Vert LPH 830 1050
Diagonal LPH 800 900
Canon PowerShot S10 Horiz LPH 850 1150
Vert LPH 850 1100
Diagonal LPH 700 n/a
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.

A good performance for such a small camera, we noted that resolution was getting close to the S10 and better than the (now ageing) Coolpix 950. The IXUS v we had for review showed a certain amount of softness on the left side of the frame.

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