LED Wall shows incorrect colours (gamma correction) after Camera Calibration
FAULT CONDITION:
We have encountered an issue where following 'camera calibration' of an LED wall, the display appeared washed out, with muted colour rendering.
This is typical of incorrect gamma correction and indeed this was the cause,even though the Novastar controller was reporting the supposedly correct value on the front panel display.
Normally this value will be around 2.8 for LED displays, but when the NovaLCT and NovaCLB has completed the calibration process it can sometimes leave the display looking as shown in the images below.
CORRECT (Original content) INCORRECT (on screen display)
The 'live' values of some parameters controlled by the software through through the API (either via Ethernet or by USB) may not be reflected in the front panel display of the controller. In this example, the controller shows that the Gamma value is 2.8, but internally the processor is still working with a different value (possibly 1.0).
SOLUTION:
To restore the correct operational value, simply access the value through the menu system, change the value to something other than the value displayed (e.g. 2.7), then dial back in the correct value (usually 2.8, but check with display manufacturer).
We have found that sometimes this does not work and that having set an incorrect gamma value, using the front panel to then restore the supposedly correct setting causes image corruption on the display. Reloading the .rcfg file to each cabinet rectified this problem (should not be necessary but maybe a quirk of some combination of firmware/hardware - Novastar bug?)
NOTES:
We have previously noticed similar faults with incorrect values - one example being a panoramic wall that was driven by 2 Novastar controllers, one controller for the left half, the other for the right. It was seen that although both controllers reported a screen brightness of 55%, there was a slight but discernible difference between the two sides. Changing both controllers from their displayed values and back again restored a seamless image brightness across the middle of the wall.
We presume this could be the case for any value accessible through the front panel controls, including Contrast, Saturation, Colour Temperature, etc.
Always make a note of the original value before overwriting/toggling away and back, so as actual changes can be easily checked and verified.
If a redundant controller is in use, remember to apply the SAME changes to the backup unit!