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Calibrate a display

Use this page to calibrate a display: ViziCAL measures it with a photometer and corrects it so it meets your chosen display standard.

How the calibration works depends on what the computer is used for. You chose this when you set up the computer (see I want to use this machine for: in Calibration Settings):

  • Radiology: the display is corrected to the DICOM grayscale standard display function (GSDF), so greys look the same on every display.
  • Colour Medical Photography: the display is corrected for colour accuracy against the sRGB standard.

Before you start

  • The display has been switched on for at least 30 minutes, so its brightness is steady.
  • The room lighting is as it normally is when people read images.
  • Your photometer is plugged straight into the computer, or the display has a built-in photometer.
  • The display's standard is set in Settings → Display Standard. See Display Standard.
  • Close anything that changes the screen's colours, such as other calibration software or a "night light" setting.

Note

During a calibration, ViziCAL needs the display and photometer to stay as they are. If a display is connected or disconnected, the display setup changes, or a USB photometer is plugged in or out, ViziCAL stops the calibration, puts the display back as it was and tells you why. Start again when everything is connected the way you want.

Calibrate a radiology display

  1. In the Displays list, find the display.
  2. Click Start Calibration on its card.
  3. If ViziCAL asks you to choose a photometer (Select photometer configuration:), choose the external photometer or the display's built-in one, then click Next.
  4. If ViziCAL finds a compatible LG display, choose how to apply the calibration. LG Monitor (Recommended) stores the calibration in the display itself. ICC Profile stores it in Windows. Click Next.
  5. When the screen says Place Photometer Over Black Square, hold or hang the photometer flat against the screen, over the black square. Skip this if you're using a built-in photometer.
  6. Click Start Calibration.
  7. Don't move the photometer, touch the display controls or use the computer until the calibration finishes. ViziCAL shows a series of grey patches and measures each one.

The calibration screen asking you to place the photometer over the black square

What happens during the calibration

  1. Position check. ViziCAL flashes the patch black and white a few times to check that the photometer can see it. If it can't, you see Ensure photometer is in the center off the black square. Move the photometer and click Try Again.
  2. Settling test (first calibration of each display only). If Measure for each display is chosen in Calibration Settings, ViziCAL switches the patch between black and white a few times and times how long the screen takes to settle. It uses this wait before every reading from then on. This takes about 10 seconds.
  3. Brightness. If Adjust Lmax to target value at start of calibration is ticked, ViziCAL first sets the display's brightness to your target.
  4. Measurements. ViziCAL measures each grey patch, then works out the correction.
  5. Check. ViziCAL applies the correction and measures again to check the result.

The calibration takes about 5 to 15 minutes, depending on the number of Calibration Points in your settings and the photometer.

If your display has a built-in photometer

  • LG displays: the first time, ViziCAL needs to find where the photometer sits on the screen. A message explains this. Click Start and keep the mouse pointer off the display while it searches. ViziCAL saves the position, so you only do this once for each display.
  • WIDE displays: the display shows the measurement patches under its own photometer, so there's nothing to find. If you use only the built-in photometer, the middle of the screen shows an animation instead of a patch. Below it, ViziCAL says what it's doing (for example "Measuring grey level 12 of 52"), how long it has taken and roughly how long is left. Don't close the window: closing it stops the calibration and puts back the display's previous calibration.

If you calibrate with both an external photometer and the built-in one, ViziCAL also adjusts the built-in photometer to match the external one. This makes the automatic checks more accurate. See Match calibration of external photometer in Internal Photometer.

The calibration screen for a WIDE display, with the built-in photometer animation and progress messages

Calibrate a colour display

  1. In the Displays list, find the display.
  2. Click Start Calibration on its card.
  3. Place the photometer over the patch and click Start Calibration.
  4. Wait while ViziCAL measures the colour patches. This takes longer than a radiology calibration.
  5. When Your corrected profile is ready appears, click Save and choose where to save the colour profile.

Load the profile in your viewing software

A colour profile only works in software that supports colour management. ViziCAL can't apply it for you. In your viewing software, look for Color Management or Assign Color Profile. If there are two choices, use your new profile as the source profile and sRGB as the destination. If your software has no colour settings, ask its supplier.

ViziCAL also corrects the display's greys straight away, so it's ready to use while you set up the profile.

What you'll see

When the calibration finishes, ViziCAL applies it to the display straight away:

  • The display card shows the new Last calibrated: date.
  • The results panel and graphs show the new results.
  • The calibration is added to the History tab.

If the display doesn't meet your chosen standard, a window says This calibration does not pass your selected standard. It lists each test that didn't pass, with things to try. The calibration is still applied. Common fixes:

  • Lmax too low: turn up the display's brightness with its own buttons and calibrate again. If the display is already at full brightness, it may not be able to meet the standard.
  • Lmin or the luminance ratio: check the Target Lmin in Calibration Settings, and dim the room lights.
  • Lamb/Lmin Ratio: the room is too bright for the display's black level. Dim the room lights.
  • GSDF: use more Calibration Points, check for a newer graphics card driver, or reset the display's own picture settings.

Click Close when you've read the suggestions.

D65 colour accuracy: Advisory

The Max D65 Color Distance line shows how close the display's white is to D65. It counts towards the result only when CIE D65 colour calibration - for true tissue colour is ticked in Calibration Settings. Otherwise a value outside the limit shows Advisory in blue: the display still passes, and your web account shows a D65 advisory instead of a fail.

Next steps

Common problems

ViziCAL says No connected photometers detected
Unplug the photometer and plug it straight into the computer again, not through a hub. Then click Refresh.
ViziCAL says the diffuser is covering the sensor
Some X-Rite photometers have a cover that turns over the sensor. Turn the cover to the other side, then click Continue.
ViziCAL warns that the L'min target is below the standard
Your Target Lmin plus the ambient light is lower than the standard allows. Choose Continue to calibrate anyway, or cancel and raise Target Lmin in Calibration Settings.
ViziCAL says a target luminance is set but the display doesn't support it
ViziCAL can't control this display's brightness. Choose to continue with the display's current brightness, or set the brightness yourself with the display's buttons.
The calibration stopped and says the display setup changed, or a USB measuring device was connected
Something changed during the calibration, so ViziCAL stopped it to protect the display. Leave the displays and photometer as they are, then start the calibration again.
ViziCAL warns that LG monitors can't be told apart
Two identical LG monitors are connected by USB and don't report a serial number. ViziCAL can't tell which USB cable belongs to which display, so it doesn't use the LG USB connection for this display. Connect only this display's USB cable, then try again.
The built-in photometer didn't see the test patch
Check that nothing is covering the built-in photometer, then click Try Again. On an LG display, if it keeps failing, click Find sensor position again.

For more, see Troubleshooting.