Glossary¶

Terms used in ViziCAL and these help pages.

A¶

Ambient luminance (Lamb): Room light reflected off the display's screen, measured in cd/m². ViziCAL adds it to the display's own light when it calibrates, because that's what the viewer sees.
Automatic check: A check that ViziCAL Apply runs by itself on a display with an internal photometer, on a schedule you choose.

Calibration: Measuring a display with a photometer and correcting it, so it meets your display standard.
cd/m²: Candela per square metre, the unit of brightness (luminance) of a display.
Check: Measuring a calibrated display to confirm it still meets its display standard, without changing it.
Connected licence: How the Licences page shows a workstation licence. Its results and reports are kept in your web account while the web service is on.
CPU Key: A code that identifies a computer for activation. Support may ask for it. Treat it as private.

DICOM: The standard for medical images. Its part 14 defines the GSDF used to calibrate radiology displays.
Display mode: A picture setting stored in the display itself, such as a colour preset (6500 K, sRGB) or a picture mode. ViziProfiler measures several and recommends the one closest to your display standard.
Display standard: A set of targets and limits for displays, such as ACR AAPM or RANZCR. You choose it in Settings → Display Standard.
Dithering: A way for the graphics card to smooth the steps between grey levels.

Gamut coverage: How much of a colour space, such as sRGB, a display can show.
GSDF (grayscale standard display function): The DICOM curve that sets how bright each grey level should be, so a grey looks the same on every calibrated display. ViziCAL reports how far the display is from it as a percentage.

Illuminance: Room light falling on the display, measured in lux.
Internal photometer: A photometer built into a display, such as some LG and WIDE displays. ViziCAL can use it for automatic checks.

JND (just-noticeable difference): The smallest change in brightness a person can see. The GSDF is built on JNDs.

Lmax and L'max: The display's brightest white. L'max includes ambient luminance.
Lmin and L'min: The display's darkest black. L'min includes ambient luminance.
Luminance ratio: L'max divided by L'min: how much brighter the display's white is than its black.
LUT (look-up table): The table of corrections that calibration makes. It's stored in the graphics card, in a Windows colour profile, or in the display itself.

Native response: How a display behaves on its own, before any calibration is applied. ViziProfiler measures the native response of each display mode.

Photometer: A small device you hold against the display to measure how bright it is. ViziCAL uses its measurements to calibrate and check the display. Some displays have one built in (see Internal photometer).

Standalone licence: A licence for one computer that doesn't send results to a web account.
Status update (heartbeat): A short message ViziCAL Apply sends to your web account when Windows starts, saying which displays are calibrated.

Uniformity: How evenly bright a display is across the screen, as a percentage difference.
User check: Another name for a visual check.

Visual check: A routine check where you look at test patterns, such as the AAPM TG18 patterns, and record what you see.
ViziProfiler: A separate program you use before calibrating. It tests your displays, checks them against your task and display standard, and recommends the display mode that needs the least correction. It doesn't calibrate.

Web account: Your organisation's area on the ViziCAL website, with its licences, workstations, results and reports.
Web service: Keeps your workstations' results and reports in your web account. It's on or off for the whole organisation and charged yearly for each workstation using a licence.
Workstation: A computer and its displays.
Workstation licence: The licence the shop sells, for one workstation. Shown as Connected on the Licences page.