Casio QV-4000 Review: 15. Compared to...: Digital Photography Review

Compared to... (contd.)

Colour Chart Comparison

Now we'll use the data in our review database to compare the QV-4000 colour and resolution to three other four megapixel digital cameras: the Canon PowerShot G2, Sony DSC-S85 and Olympus C-4040Z.

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.

Casio QV-4000 Canon PowerShot G2

Sony DSC-S85 Olympus C-4040Z

All of these four megapixel digital cameras are very close for colour balance. Casio have done a good job of producing well balanced yet vivid colours. Here are some general observations:

Better overall colour balance than the C-4040Z (stronger reds and yellows)
Less saturated than the DSC-S85 (good, plus you can adjust via record menu)
Blues not quite as strong as the Canon G2
Grayscale is a little contrasty, not much detail beyond patch 15

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	Casio QV-4000	Canon PowerShot G2	Sony DSC-S85	Olympus C-4040Z
Black	21,23,25	45,43,42	17,17,19	35,36,35
Black
Middle Gray	91,92,94	107,106,110	76,81,79	111,105,110
Middle Gray
White	198,199,199	208,210,208	188,189,189	211,210,217
White
Magenta	178,14,100	196,37,116	170,12,124	190,46,110
Magenta
Red	178,4,33	195,30,35	176,0,40	178,44,45
Red
Yellow	194,176,64	205,195,20	181,180,14	191,195,65
Yellow
Green	28,129,59	43,152,68	24,131,27	41,145,84
Green
Cyan	10,141,188	23,169,234	23,158,175	52,166,220
Cyan
Blue	37,26,104	61,56,133	23,31,112	75,58,118
Blue

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 1/100^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.

Horizontal resolution Vertical resolution 5 degree diagonal res.

Casio QV-4000

Canon PowerShot G2

Sony DSC-S85

Olympus C-4040Z

Measurable findings (three measurements taken for each camera):

Camera	Measurement	Absolute Res.	Extinction Res.
Casio QV-4000	Horiz LPH	1150	*1350
	Vert LPH	1100	1400
	5^o Diagonal LPH	1000	n/a
Canon PowerShot G2	Horiz LPH	1250	*1450
	Vert LPH	1200	*1500
	5^o Diagonal LPH	1000	n/a
Sony DSC-S85	Horiz LPH	1250	*1650
	Vert LPH	1200	1650
	5^o Diagonal LPH	1000	n/a
Olympus C-4040Z	Horiz LPH	1150	*1350
	Vert LPH	1100	1400
	5^o 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)
5^o Diagonal	Lines set at 5^o 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 Casio QV-4000 matched Olympus's C-4040Z for resolution, at the lower end of what we'd expect from a four megapixel digital camera. Taking a closer look at the QV-4000's resolution chart it's clear to see that at least some of the artifacts are a result of its noise reduction algorithm, the rest has been lost in unsophisticated Bayer interpolation.

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