How we test digital cameras

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03.Functions tests

Monitor and viewfinder

The quality of the monitor and viewfinder are evaluated by a panel for readability under different light conditions (sunshine, low light indoor). Adjustments for users wearing glasses (diopter correction) is evaluated as well. In both cases we look for picture quality in terms of colour performance, brightness, contrast, resolution and the speed of the refresh rate (important for precise pictures when zooming or taking photos in panning situations)..

Viewfinder

The evaluation of the viewfinder is performed by scoring the usability in bright sunlight conditions outside, the usability in poor light conditions inside, the quality of resolution and refresh rate at panning scenes and the size of the image in the viewfinder. Basic cameras are not penalized for not having a viewfinder, but High-end cameras are.
For High-end cameras:
We measure the difference of the size of the image in the viewfinder related to the width stored in the image. The camera is positioned as close as possible to a rectangular test chart. The test chart is adjusted to full viewfinder size by adjusting the distance to the test chart at the maximum wide setting and maximum telescopic setting of the zoom lens.

Monitor

The monitor's loss of readability (contrast, brightness, colour) when viewed from an angle other than 90° from above (evaluation range is +/-30° to left and right and +/-20° to above and below related to view from right angle). This test is performed indoors in good light with no light from behind the monitor and in poor light conditions. This is repeated outside in bright conditions.
The quality of the monitor in Playback mode is evaluated using a test image in JPEG format with fine details and high contrast. Each camera tested has the test file displayed in full screen mode and without additional information (if possible), which is photographed with a high resolution digital camera. All cameras’ monitors are shot using the same focal length of the recording camera, so that different sizes of the file image show the different size of the display. These shots of the tested cameras monitors are evaluated on a high quality PC screen for resolution, sharpness, contrast and brightness of the display as well as some other errors such as a visible cell structure of the LCD panel.
In this test only the quality of the monitor itself is evaluated. In the tests previously described the cameras are in record mode, which means that the effects of the image sensor, the lens and the exposure electronics also have an influence on the result.
The following pictures show some examples of different monitor displays.

Poor monitor Middling monitor Good monitor

Image stabilisation

Image stabilisation rigThe test signal is recorded from acceleration sensors applied the arms of two men holding a camera in their hands at a normal shooting position. This signal is averaged for the two persons and measured over a lengthy period. We test by mounting the camera on a shaker and applying the recorded movement in different directions and at different strengths while taking images. Half the images are taken at normal viewing angle (47°) of an 80cm target at around one meter distance. This is done with a light level of 11 Lux and the cameras flash is turned off. Where possible the test is repeated with the lens set to a viewing angle of 12°, which puts the target at around four meters from the camera and the light level is adjusted to 1000 Lux.

Focusing

A score is given for the autofocus behavior in a room with an illumination level of 11 lux, with flash suppressed for; speed of focus, ringing, a stable final setting and sharpness of the images.

Autofocus Sensitivity (High-end cameras only)

We take an image in automatic mode and at normal focal length (image angle ≈ 47°) of a test chart at a distance of one metre illuminated by photo lamps. There's a pattern in the centre of the screen to allow the camera to focus automatically. The power of the photo lamps is reduced which in turn reduces the contrast of the pattern on the test chart. We measure the luminance of the test chart in cd/m² when the auto focus doesn't reliably find the focus point any more.

Macro image

The macro function of the camera is performed by measuring the smallest sharp area which the camera can take in macro mode. We also measure the distance between test chart and lens front. The test is performed using automatic focus.

Flash

We check to see if the flash is "intelligent" (the power of the flash is adapted to the distance from the subject automatically).
Flash quality Flash targets
A picture of the test chart is taken in a dark room. The camera is adjusted to fit to the full test chart in the viewfinder/monitor of the camera by using the zoom lens.
Pictures are taken at one, three and five metres.
The resulting images are appraised for the amount of light put out by the flash, evenness of illumination and ability of the flash to cope with varying distances. If necessary we also Flash evennessnote reflections/shadows from the camera's body.
Flash quality long distance
A complete dark room with white walls has distance marks (small grey cards) at different positions within the room. Their brightness is evaluated for the flatness of the distribution of the flash light across the scene.

 

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