Black or gray object that reflects the same light intensity whatever the viewing angle or light source angle (not glossy).
Artifacts in images, with a maze shape, due to errors during demosaicing.
Exposure levels corresponding to medium gray levels on the sensor.
Modulation transfer function
Function describing the ratio between the amplitude of a pure frequency signal before and after a system as a function of the frequency.
A metric is a lens or camera sensor image quality performance characteristic selected for analysis on DxOMark. There are three Metrics for scoring camera sensors (Color Depth, Dynamic Range, Low-Light ISO), and five Metrics for scoring lenses (Resolution, Distortion, Vignetting, Transmission, Chromatic Aberration).
Read more about Lens Metric definitions and Sensor Use Case definitions (Metrics and Use Cases are equivalent for sensors).
Megapixel, a million pixels.
Portrait & Studio (use case)
Part of a measured signal which is different from the original signal. In an image, noise is especially visible in uniform areas
Noise covariance matrix
For a multichannel image, matrix giving the covariance of the noise in the different channels.
Random variations of the light perceived by the sensor due to the fact that photons are not emitted at a constant rate, but follow a random process (see Poisson process).
Pixel response non-uniformity. Noise due to the inhomogeneity of pixels properties on the sensor.
Peak Score (former score for lens with camera)
The term "Peak Score" is not used anymore on DxOMark. Ranking used to be provided using this Peak Score; now ranking is provided using the DxOMark Score.
Former definition of Peak Score (now renamed as Mid-Light Score and shown in the lens measurement page):
The Peak Score is the performance of a lens (with a camera body) for its best focal length and aperture combination. Therefore, it does not show how the lens behaves over its entire focal range. Other lens scores, such as Use Case and Optical Metric Scores, report average performances over the whole focal length and aperture ranges.
Also, the Peak Score is measured for defined exposure conditions corresponding to typical studio photography with 5,000 lux illumination and an exposure time of 1/125s.
Algorithm aiming to retrieve the part of the signal directly related to the scene
Noise, thermal [electronic]
Also known as dark current noise. Part of the noise due to thermally generated free electrons. It is currently considered that thermal noise doubles for an increase of 8° of the ambient temperature. This noise is particularly visible in low-light.
Action of changing numerical values with respect to a given reference in order to facilitate comparison between, for example, cameras having different sensor resolutions or sizes.
Results obtained after several mathematical transformations, used to easily compare systems with different characteristics, as camera resolution, pixel pitch, etc.
Axis of symmetry of an optical system, usually set at the center of the picture.
An exposure that is too important, resulting in burnt highlights.
Portrait Score (based on Color Depth)
The Portrait Score is defined as the color depth performance and its unit is a number of bits.
A color depth of 22bits is excellent, differences below 1 bit are barely noticeable.
This score is named "Portrait" because generally what matters most when shooting portraits is to aim for the richest color rendition.
Read more about Portrait Score.
Photography, silver halide
Photography using traditional film composed of chemical components and silver ions.
The elemental particle of light. It has a zero mass, travels at light speed, and is characterized by its wavelength.
Part of a sensor that receives photons. Each photosite corresponds to a pixel at the end of image processing.
Picture element, the smallest element of a digital image.
Pixel, hot, dead
A pixel (or photosite) whose response to light is very different from the mean response of the other pixels on the sensor. They produce small but very visible artifacts on an image.
Width of a pixel on a sensor, expressed usually in µm.
Pixel response non-uniformity
Stochastic (or random) process modeling queuing phenomena. It is a good model of photons arrival on a sensor.
Taking close-up photos of people, generally in a controlled environment (such as a studio).
Dispersion of light: different wavelengths are refracted with a difference angle, like a rainbow.
The set of procedures used to measure characteristics of a camera.
The Mid-Light Score is the average performance of a lens with a camera body the different focal lengthfor a defined exposure conditions.
It is equivalent to the DxOMark Score except that it is based on mid-lighting conditions (5,000 Lux and 1/125s exposure time). Mid-Light Score makes a lot of sense when evaluating lenses with camera used in good lighting conditions: particularly appropriate for medium-format cameras used in studio environments.