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.
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.
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|
|Nikon Coolpix 950|
Measurable findings (three measurements taken for each camera):
|Camera||Measurement||Absolute Res.||Extinction Res.|
|Canon Digital IXUS
(S110 Digital Elph)
|Horiz LPH *||830||1000|
|5° Diagonal LPH||800||900|
|Canon PowerShot S10||Horiz LPH||850||1150|
|5° Diagonal LPH||700||n/a|
|Sony MVC-CD200||Horiz LPH *||850||1050|
|5° Diagonal LPH||800||900|
|Nikon Coolpix 950||Horiz LPH||750||1050|
|5° 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.