micro:bit display pixel brightness

Hello Gordon,
thank you for your reply!
I've tried a couple of things, but I suspect the switching via setInterval is not fast and/or precise enough.
Here is what I've tried so far (trying to get all pixels at 50% brightness):

setInterval(function(){
 show(0x1FFFFFF);
 setTimeout("show(0)", 10);
},20); 

and this one:

var c = 0;
setInterval(function(){
 if(c%2===0) show(0x1FFFFFF);
 else show(0);
 c++;
},10); 

I thought the last one would be a little bit faster (by removing setTimeout) but nothing changed.

As for a firmware mod, this would be awesome of course!
A nice way to implement it, would be perhaps in your graphics library, while creating the ArrayBuffer:

g = Graphics.createArrayBuffer(5,5,4);

this way we could manage images with 16 levels of gray/brightness directly.
Would this make sense?

The micropython firmware supports 9 levels of brightness (0 is off) and visually it works pretty well, the other official firmware (the js/typescript thing) "supports" 255 levels of brightness, but this really does not work, and all kind of weird things happen (probably the out-of-phase problems you mentioned?)