How we test digital cameras

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04.Video tests

Video viewing test

Monitors, projectors and video cards are adjusted to sRGB colour space. All measurements and recordings are made using automatic exposure and automatic white balance settings. Two one minute video recordings are made of a scene featuring people with colourful clothes, other objects with fine details and realistic artificial plants at different distances, both at rest and in motion. The automatic focus system and white balance is switched on – if possible. The camera is mounted on a tripod, about a third of the take is recorded while panning and another third while zooming. Lighting for the tests is under the following lighting conditions at the targets:
- Daylight conditions, 3500 Lux (D65)
- Low light, 12 Lux. A scene from video testing
These recordings are replayed on profiled and calibrated, high-quality liquid crystal monitors or projectors with high resolution (FullHD with 1920 x 1080 pixels and at least 25 (24) frames per second). The test panelists evaluate colour fidelity, the test persons are allowed to observe the actual objects (colourful objects and the like) used in making the recordings with appropriate illumination. The recorded images are rated according to the following criteria:
1. Sharpness (how faithfully structures are reproduced)
2. Colour fidelity (colour neutrality and colour noise)
3. Exposure and contrast gradation (also in highlights and in dark areas)
4. Overall image quality
4. Image and focusing irregularities.

Resolution

We take video recordings at maximum and minimum focal length of the same test chart used for still images and rate them for the resolution of the images at the centre and corners.

Macro Recording

We take video recordings at maximum magnification and rate them for the resolution and the overall quality of the images. Paying particular attention to any issues with focusing, exposure or contrast etc.

Audio Quality

All measurements and recordings are made using the cameras automatic gain control settings. An audio stereo sample from CD (classical music with high dynamic range), with a duration of about 30 seconds is played over two high-quality loudspeakers in a room. First, a reference recording from these samples is produced on a digital recorder with a high-quality stereo microphone at a distance of two metres. The sound pressure level at the location of the microphone is at an average of 65 dB(A). Two audio recordings are made with each camera being tested, under the same conditions. Recording is done using the built-in microphone in automatic mode and we create possible noise by using the zoom button or zoom drive.
We then listen to the recordings using high-quality headphones and rate the “overall audio quality” of the sample recordings, at the original volume. Problems with motor-, zoom- and button-noises are commented on separately.

Device ready for operation

The device is switched off for at least a minute then switched on and we measure the time it takes before the first video frame is taken.

 

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