Well, the camera pic you get inside gtkradiant is just an approximation... it doesn't actually do any lightmapping so it'll never be quite right.

You said you didn't use any lights in your map? Or did you compile it in gtkradiant without lights? hrmmm...

ok, lemme start over. The textures you're using, do they have shaders or are they just straight textures? Easiest way to tell is in the texture picker, do they have a white outline? If not, they're just plain textures, otherwise they have a shader. If they have a shader, the shader may be creating the light.

If they don't have a shader, then you have to have some sort of light in there. It may be a light entity, or it may be a shader that produces light nearby. Thing is, if you compile your map with no light entities and no light-emitting textures, then your map should be completely and utterly black. Unless your world has an ambient light setting, which is really a no-no.

Last thing is that you may have compiled your map without telling it to do the light map. Basically, you want bsp -fullvis -vlight (or something like that). Rendering it without doing the lightmap will cause lighting to be wrong.

So, IMO, it's either...

1. too many/too bright light entities
2. too many/too bright light-emitting shader
3. the world has an ambient light value
4. compiled without rendering the lightmap

Basically, it has to be one of those, otherwise your map would be pitch-black. I hope this helps.