Changing the LED Brightness

Does anyone have an example of changing the LED brightness?

I’m using Matrix OS and am playing with this example

var counter = 0;
setInterval(function(){
        matrix.led({
                color:'red',
                arc:120,
                start:0
        }).rotate(counter).render();
        counter++;
},2);

But I can find any documentation on how to change the brightness.

I’ve tried the .darken option but it seems to not work

Thanks

‘color’ accepts CSS so you can do #660000 for a darker red. in my experience, you can get away with #330000 just fine for most purposes. the colors aren’t perfectly accurate, unfortunately.

an undocumented option is also to start MOS with SUN_MODE=true to enable the white leds and luminance calculations, but this is intended to operate behind a filter of some sort, because it’s blindingly bright.