Glossary

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I3A, I3A-CPIQ

International Industrial Imaging Association: www.i3a.org. CPIQ stands for Cameraphone Image Quality, an I3A initiative to define standards for measuring cameraphone image quality.

Illuminant

Spectrum of a light source, sometime expressed as Correlated Color Temperature.

Illumination, illuminance

Intensity of incoming light on an object, expressed in lux.

Image processing

Set of theories, methods and algorithms for manipulating digital images

Incertitude ellipsoid

The set of noisy values that are likely to be measured around the average of a multichannel signal. By convention, it usually corresponds to a single standard deviation.

ISO (international organization for standardization)

Abbreviation of International Organization for Standardization, the world's largest developer and publisher of international standards of measurement.

ISO speed

Sensitivity of a camera, refers to ISO 12232 standard

ISP (image signal processor or processing)

Set of algorithms for transforming a RAW sensor image into a RGB image that can be visualized by a user.

JPEG

Abbreviation of Joint Photographic Experts Group, the name of the committee that created a standard for still image compression.

Landscape & Architecture (use case)

Landscape & architecture photography commonly involves mounting the camera on a tripod and using the lowest possible ISO setting to minimize noise, thus maximizing image quality. In addition, photographers typically use short focal lenses, as they need to capture an entire structure or landscape. Read more about Lens Use Cases and Sensor Use Cases definitions.

Landscape Score (based on Dynamic Range)

The Landscape Score is defined as the maximum Dynamic Range of the camera sensor and its unit is an exposure value (EV).

A value of 12 EV is excellent with differences below 0.5 EV usually not noticeable.

This score is named "Landscape" as contrasts are typically very high in landscape photography and it's therefore critical to have wide dyanamic range for such use.

Read more about Landscape Score.

Lateral chromatic aberration (LCA)

When a lens exhibits lateral chromatic aberration, the image of a perfectly sharp edge going from white to black shows color fringes (mostly purple, blue, or red) on the border of the edge. This is because simple lenses, like prisms, do not focus the different wavelengths of light on the same image plane. Read more about how LCA is defined, measured and scored.

Lens

Optical component that causes light to converge or diverge; by extension, an optical system.

Lens Metric Scores (or Optical Metric Scores)

DxOMark reports lens performance Scores for five Lens Metrics, each having its own unit of measure: Sharpness (P-Mpix), Distortion (%), Vignetting (EV), Transmission (T-stop), Chromatic Aberration (µm scaled on a 24x36mm sensor).
Read more about scoring Lens Metrics.

Lens Use Case Scores

DxOMark reports lens performance Scores for five Use Cases: Travel & Family, Portrait & Studio, Sports & Wildlife, Reportage, and Landscape & Architecture. The Lens Use Case Scores are provided on a 5-star scale. When a lens does not have the focal length or aperture range for a given Use Case, it is reported as "not applicable".
Read more about Lens Use Case Scores.

Logarithmic scale

Scale in which an increment of 1 corresponds to a multiplicative factor (10 for log10, 2 for log2). For example, the EV (exposure values) scale is a logarithmic scale, doubling the exposure corresponds to EV+1.

Low gain

Low sensitivity (see Gain).

Low-light ISO

The maximal value of ISO sensitivity needed to reach a given value of Signal-to-Noise Ratio. The greater the value, the better.

Luminance

Unit describing the amount of light passing through a given area and falling in a given solid angle, expressed in cd/m².

Luminance meter

Device that measures luminance (cd/m²).

Lux-meter

Device that measures illuminance (lux).