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Settings: Calibration Settings

Use this page to choose how ViziCAL calibrates and checks your displays.

Open Settings → Calibration Settings.

Common Controls

These apply to every display.

  • Share calibration settings for all displays: use one set of settings for every display. Untick it to set each display separately.
  • Uniformity check - beep to move: beep when it's time to move the photometer during a uniformity measurement.
  • Notify on changes in display settings: warn when a display's own brightness, contrast or picture mode changes, because this can make the calibration wrong. See ViziCAL Apply.

Wait after each patch change

After ViziCAL changes the patch on the screen, the display takes a moment to settle at the new brightness. If ViziCAL measures too soon, the reading is partly of the previous patch. This matters most for dark greys.

  • Measure for each display (recommended): the first time a display is calibrated with an external photometer, ViziCAL switches the patch between black and white and times how long the screen takes to settle. It waits that long, plus a margin, before every reading on that display from then on. Built-in photometers can't time this, so they use the fixed wait.
  • Fixed: wait the same time on every display. Type it in milliseconds in ms fixed wait, between 100 and 3000. The default is 300. This time is also used until a display has been measured.

Below the options, ViziCAL says how many displays have been measured. To measure every display again at its next calibration, for example after changing its picture settings, click Measure Again at Next Calibration.

X-Rite Photometer Calibration Profile

X-Rite photometers can be matched to the type of backlight in your display, such as white LED or wide gamut. Plug the photometer in, click Refresh, then choose the profile that matches your display. If you're not sure, ask your display supplier.

Display settings

Under Calibration Settings, choose the display at the top (unless settings are shared).

I want to use this machine for: sets what the computer is used for:

  • Radiology: calibrate to the DICOM greyscale standard.
  • Colour Medical Photography: calibrate for colour accuracy.

Radiology settings

  • CIE D65 colour calibration - for true tissue colour: also correct the white to D65, so greys look neutral and several displays match. When it's ticked, D65 colour accuracy is part of the calibration and check results: a display outside the D65 limit fails. When it isn't, a D65 miss is only an Advisory.
  • Calibration Points: how many grey levels to measure when calibrating. More points are more accurate but take longer. 65 Samples (DICOM recommended for calibration) or 52 Samples (AAPM TG270 recommended for calibration) suit most displays.
  • Verification Points: how many grey levels to measure when checking. Use 18 Samples (VALID for Certification Check): ViziCAL scores GSDF conformance only with 18 samples.
  • Colour dithering mode: how the graphics card smooths steps between grey levels: Full, Partial or None. Use None if colours look wrong.
  • LUT bit depth: the precision of the correction. Match it to the graphics card's output, for example 8-bit or 10-bit.
  • Luminance Targets:
    • Target Lmin (cd/m2): the black level you want. With the room's ambient light, it sets L'min (L'min = Lmin + Lamb). If it's below what your standard allows, ViziCAL warns you before calibrating.
    • Target Lmax (cd/m2): the white level you want.
    • Adjust Lmax to target value at start of calibration: set the display's brightness to Target Lmax before calibrating. This needs a display whose brightness ViziCAL can control.
  • Rollback to last calibration settings: undo setting changes made since the last calibration.

Colour settings

  • Number of Calibration Samples: how many colours to measure.
  • Output Accuracy: the size of the colour correction. Larger is smoother but takes longer to work out.
  • Gamma Curve Measurements: how many grey levels to measure for each colour channel.
  • Check Set: the colour patches used to check accuracy after calibrating.

The table at the bottom lists the settings of every display.