The option is always there, but it only makes a difference if you have units DSABed together. The goal here is to have different brightness screens APPEAR the same, since for a given backlight level, a super-bright screened unit is about twice as bright as a regular unit. Practically speaking, this only matters at night.
Sometimes it'll kick the brightness down a notch when you choose the option. What you can do to absolutely ensure everything is in sync is to individually set each screen's option, then recycle power to everything, and then to a fresh DSAB configuration.
Text from the manual...
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Brightness Configuration
In a DSAB network, changing the brightness level of one instrument affects all connected
instruments. Dynon Avionics sells D100-series instruments with both regular and bright screens.
Each instrument connected to your DSAB network must have its display type configured to
ensure that perceived brightness matches across all screens. To do this, enter the SETUP >
DSAB > BRIGHTNESS menu on each product in the system. If you purchased the bright screen
option for your FlightDEK-D180, press TOGGLE to change the BRIGHT SCREEN status to
YES. Otherwise, ensure this is set to NO.
If the DIM setting of one of the screens in a DSAB network gets “out of sync” (some
dim, some bright), this can be corrected by adjusting the DSAB Bus Master screen to the
desired DIM and then performing a DSAB CONFIGURE.
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