HP Photosmart 850 Review: 15. Compared to...: Digital Photography Review

Compared to... (contd.)

Now we'll compare the HP Photosmart 850 to a few other four megapixel digital cameras from our test archives. Here we're comparing color and resolution to the Canon PowerShot G3, Nikon Coolpix 4500 and Sony DSC-S85.

Color Chart Comparison

Color charts are shot in daylight, Auto White Balance, EV compensation +0.3 (except the 850 which only has 0.5 EV exposure compensation steps), measured light ~10 EV. This test is also dependent on the accuracy of the camera's auto white balance, the color 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.


HP Photosmart 850 *	Canon PowerShot G3

Nikon Coolpix 4500	Sony DSC-S85

* The HP 850 image appears brighter because it only allows 0.5 EV exposure compensation steps, not our normal 0.3 EV.

In the table below we're only measuring color. The RGB values were measured from a VGA reduced image (to average colors, remove noise and eliminate JPEG artifacts) using the Eyedropper tool in Photoshop with a 5 by 5 Average Sample Size.

Patch	HP Photosmart 850 *	Canon PowerShot G3	Nikon Coolpix 4500	Sony DSC-S85
Black	36,35,38	34,34,34	25,27,27	17,17,19
Middle Gray	130,129,127	102,105,105	101,100,102	76,81,79
White	255,254,252	212,212,212	211,210,209	188,189,189
Magenta	254,36,129	208,45,115	203,38,118	170,12,124
Red	254,27,55	203,34,44	189,22,43	176,0,40
Yellow	255,244,80	208,192,30	193,183,27	181,180,14
Green	0,160,102	23,138,73	29,140,61	24,131,27
Cyan	0,171,231	5,152,218	60,167,205	23,158,175
Blue	28,36,116	37,49,122	54,47,112	23,31,112

* The HP 850 image appears brighter because it only allows 0.5 EV exposure compensation steps, not our normal 0.3 EV.

It's pretty difficult to make any serious comparison when we can't reproduce the same exposure as the other cameras, that said you can see that the shade of each patch is approximately the same as the other cameras. The difference between 0.3 and 0.5 EV exposure compensation is enough to push several of the patches to clipping on the 850.

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 1/100^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 (to compensate for the white background).

Horizontal resolution	Vertical resolution	5 degree diagonal res.

HP Photosmart 850

Canon PowerShot G3

Nikon Coolpix 4500

Sony DSC-S85

Measurable findings (three measurements taken for each camera)

Camera	Measurement	Absolute Res.	Extinction Res.
HP Photosmart 850	Horiz LPH	* 1200	1350
	Vert LPH	1100	1350
	5° Diagonal LPH	1000	n/a
Canon PowerShot G3	Horiz LPH	1250	1400
	Vert LPH	1200	1400
	5° Diagonal LPH	# 1000	n/a
Nikon Coolpix 4500	Horiz LPH	* 1200	* 1350
	Vert LPH	1100	1300
	5° Diagonal LPH	1000	n/a
Sony DSC-S85	Horiz LPH	1250	* 1650
	Vert LPH	1200	1650
	5° Diagonal LPH	1000	n/a

* Moiré is visible, # Jagged edges to diagonals

Definition of terms

LPH	Lines per Picture Height (to allow for different aspect ratios the measurement is the same for horizontal and vertical)
5° Diagonal	Lines set at 5° 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.

All things considered the HP 850 puts in a respectable performance, at least as much resolution as the Nikon Coolpix 4500, although with possibly more visible moire and some artifacts. This is a fairly impressive performance considering that the HP 850 only represents the second generation of HP's new line of digital cameras, at least they are moving forward.

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