Real-time Lighting vs Lightmap
Reflex has two main modes of lighting. Real Time and Baked. Whenever you edit your map you are in real time mode. Real time lighting shown in the following screenshot from the map Deflex.
Real-Time lighting is always at a fixed brightness level. It does not matter if you use artificial lighting or ambient lighting. The lighting will perform practically the same no matter what you attempt to do. Even if you build a small box and put yourself inside the box you will still be able to see everything perfectly. This is because real time lighting is very handy for map editing so you can see everything and every where in your map. You can still have real time shadow generation but it is not as dramatic as a baked lightmap would provide.
A built lightmap is also known as baked lighting. You build a lightmap using the console command of r_lm_build. If you have absolutely no light sources (artificial or ambient outside light) in your map and you bake a lightmap everything should be pitch black like you are in a dark closet. You cannot even see the gun in front of you. That is the definition of a well baked lightmap. Lighting is usually one of the last steps in map building because it can cause new map designers the most amount of trial and error. You will never likely design a map with perfect lighting your first attempt. You will have to build the lightmap, see what lights need to be moved or placed, then rebuild the lightmap. You will find yourself repeating that process over and over until you get it just how you want the map to appear to a player. Ensure you have at least some lighting prior to building your lightmap either outside ambient light or artificial lights otherwise you will not be able to see anything when the lm build completes.
This is an example of exactly the same location shown after baking the lightmap. This is a great example of what a baked lightmap looks like in dark conditions with inadequate lights. The screenshot is dark on purpose to show that only baked lightmaps can achieve darker mood lighting that real time lighting cannot provide. Including baked lightmaps can help speed up connection times otherwise real time lighting has to be generated by each players GPU. Real time lighting is slightly more intensive than a built lightmap.