Experienced modders might already know it, but for those who don't this image shows a correlation between a surface's lightmap scale (set in Hammer and used for vrad calculations) and a shape, brightness and overall quality of a spot of dynamic light cast onto the said surface. As you can see, the effect gets most bright on the 8x scale (although it's the matter of item's position, there's no really significant difference between 4x and 8x), it gets a bit diffused on 16x (a default value for most surfaces in HL2/Episodes and in Hammer), and on 32x it is just a big dim square not practically aesthetic. If the light spot will be bigger, it would turn into a very rough circle with jagged edges.
So if you add the dyn. lighting effect on your map or implement it in your code, like muzzleflashes or burning NPC light effect, be sure to set the lightmap accordingly.
Huh, interesting. Thanks for comparison!