Brompton Technology has announced new Dynamic Calibration enabled features for its processors at LDI 2019, including ThermaCal, which eliminates thermal patterning on hot LED panels, and PureTone, which eradicates unsightly colour casts in low brightness greyscales for a balanced, neutral output.
LEDs are affected by temperature and all tend to be a bit less bright as they get hotter. But the scale of this effect varies between colours, with red LEDs most strongly affected: heat a red LED by 10 degrees and its output typically drops by 10%.
Because of this difference in effect between LED colours, areas that are hotter or colder than the temperature the panel was calibrated at can show a colour shift. What is more, panels often heat up more in the centre than round their edges, which can lead to unsightly thermal patterns that mark out individual panels in the wall. ThermaCal compensates for these effects and gives the user control of how much compensation is required based on the panel temperature and environment.
It does this by both separating thermal effects from the optical calibration and by profiling each panel type to understand in detail its thermal characteristics for a smooth, panel-specific correction. The amount of correction can be adjusted dynamically, even during a show, to account for changes in temperature over time.
LEDs and their driver chips are not perfectly linear, meaning that when asked to output a particular brightness they may not accurately achieve it. It is common for the red, green and blue LEDs to have different behaviour, meaning that many panel types show a colour cast in darker greys or when using the panels at low brightness levels.
Most content has dark as well as light areas, so this non-linearity is a real problem that means you may not be getting accurate colours and true neutral greys. It is also a common reason why different panels that appear to be matched when displaying full brightness test patterns are obviously unmatched when displaying real content with darker areas.
Previously, it has been difficult or even impossible to correct for this non-linear behaviour.
PureTone builds on Brompton’s new Dynamic Calibration technology to enable each panel type to be profiled in order to compensate for the non-linearities ensuring true, clean, accurate colours and neutral greys at all brightnesses.
This is particularly important for film and broadcast work, where screens are often run at much lower brightness to match camera exposures, and maintaining neutral colour output is critical to looking good on camera.
PureTone depends on Dark Magic – which improves the quality of the image or video showing on LED panels when they are operating at less than maximum brightness – for additional effective bit depth in order to make very small fractional adjustments to the output drive levels. It also works alongside ThermaCal.
Both ThermaCal and PureTone are exclusive to Brompton R2-based panels that are enabled for Dynamic Calibration.