DxOMark measurements for lenses and camera sensors
News| Introduction | ISO sensitivity | Noise | Color sensitivity | Sharpness | Distortion | Light transmission | Vignetting | LCA |
What is vignetting?
Vignetting or light shading consists of the attenuation of light far from the image center.
There is a natural cause of vignetting: An object that is off-axis “sees” the aperture with a smaller solid angle (the apparent surface of the aperture stop as seen from the object’s position). For large-aperture lenses, another phenomenon also impacts the illumination of the sensor in the image. In these cases, not all rays from an off-axis element that go through the stop of the lens will reach the sensor. Some of them will be blocked by mechanical elements inside the lens.
What does DxOMark measure?
DxOMark measures light vignetting by imaging an evenly-lit white target. Pixel values are retrieved from all parts of the image. The ratio of these values over the maximum value (usually the value at the image center) found in the image gives the vignetting measurement for each pixel. Vignetting is expressed in exposure value (EV): a variation of 1EV is an attenuation of a factor of 2.
We create a field map of the vignetting as well as an average radial profile.
We then extract a statistic such as the maximum value of vignetting found in the image, and then map it as a function of focal length and aperture value.
DxOMark displays the vignetting profile as a function of the distance to the image center. There is a profile for each focal length and f-number.
Vignetting is mapped in the image field. To facilitate comparison, attenuation is quantized every 1/3EV. There is a map for each focal length and f-number.
Further readings for the DxOMark measurements for lenses and camera sensors
To provide photographers with a broader perspective about mobiles, lenses and cameras, here are links to articles, reviews, and analyses of photographic equipment produced by DxOMark, renown websites, magazines or blogs.
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The Nikon D5000 and the Canon EOS 500D were two main releases for spring 2009. Launched at the same time, and targeting the same market, these two cameras were the perfect subjects to use for an extensive demonstration of the DxOMark Database. |
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A detailed look at DxOMark's image quality testing protocols, including laboratory conditions and setup, methods, test-specific tools, and software that DxO Labs developed and uses to ensure scientific, bias-free data and repeatable results. |
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On DxOMark, we evaluate and rank many types of digital cameras with image sensors that vary widely in pixel count, pixel size, and digital signal processing. To ensure that sensor performance comparisons between cameras are fair, it is very important both to test under identical shooting conditions and to take viewing conditions into account. |