© 2021 Flanders Scientific, Inc.
20
Understanding Modulation Modes
The XM310K is a zoned backlight monitor featuring a full array local dimming (FALD) backlight with
over 2000 LED zones. The advantages of FALD backlights are that they remain one of the most effi-
cient, practical, and cost effective ways to achieve very high peak luminance as well as very good black
levels. The behavior and visual quality of any zoned backlight system are regulated both by the number
of zones and the performance of the display’s backlight/LCD driving algorithms.
Generally speaking, displays with a higher number of individually controllable zones will outperform dis-
plays with a lower number of individually controllable zones. A display like the XM310K with over 2000
zones can therefore be expected to outperform displays that may only have 500 zones. This comes
down to simple physics as more zones means finer tuned control over regions of the display. However,
it is also important to consider the behavior of the human visual system as there is a point of diminishing
returns as backlight density increases. Bright objects do result in a degree of veiling glare in the human
eye so our ability to discern local contrast (sometimes called point spread function), especially in HDR,
is not necessarily the same as the resolution of the display. This is ultimately very content and adaption
state dependent so it would be an overgeneralization to suggest that one particular zone count is the
perfect solution for all scenarios. Displays with near perfect pixel level luminance control are of course
the ideal target and there are in fact displays that essentially achieve this (OLED and LMCL for exam-
ple), but typically at the cost of other performance benchmarks like peak luminance to name just one
potential limitation.
The backlight algorithms that drive a FALD display will necessarily need to compromise between differ-
ent aspects of display performance. To minimize the appearance of halation for example the backlight
algorithms may dim highlights or globally lift black levels. Or conversely the algorithms may maximize
peak luminance response of even small bright objects at the cost of halation or flare. Most consumer
displays and many professional displays have only one algorithm mode in place. This is not to say that
the algorithm behavior doesn’t adjust based on content, but ultimately there is often no way to force
specific behaviors that might be incredibly important in a professional mastering context. The XM310K
is built for use in a professional mastering environment and as such has three manually selectable
backlight modulation modes accessible to the operator to prioritize different viewing needs.
Peak
The Peak optimized modulation mode ensures the peak highlight code values are represented accu-
rately on screen even if this results in some halation or flare. To put this in context if you have a black
background with just a few bright pixels present with code values representing 3000nits they will be
shown at 3000nit nits in Peak mode with the side effect of a halo around those bright pixels. The value
of the Peak optimized modulation mode comes in QC applications where operators want to ensure that
highlight details contain the information they expect. The backlight algorithm behavior of many other
FALD display devices may hide important small bright object highlight detail with no way to switch to
a mode like Peak to see highlight code values represented accurately. Peak is the mode we find most
colorists use for grading any given scene. Because Peak Modulation mode prioritizes accurate code
value representation above all else it is also the mode that should be used for calibration verification.
