When I disable it the radius gets really big, more or less the way I want it, but I didn't get what you said about the set opacity thing. I just copied from the example file. What I understood is that code makes it so that the opacity is set in relevance to its distance from the light source, but only up to a certain distance. Is this right? If so, how can I change what the restraint is?
The equation I used for the opacity was a quick implementation.
The radius say 5 is multiplied by the tile size which is default 32. This is the maximum distance at which the opacity would be 100 or 0 depending on how you blend the LightCell/Shadow. You need to gradually decrease/increase this as the distance decreases back to the centre. Plus a realistic light has more of a drop off than a linear reduction in intensity. There is a bit of math involved in producing a realistic light. Experiment.
Quick and easy way: min(Distance from light to shadow cell / (Radius * Tilesize), 1) this produces a number between 0 and 1. To invert take this number from 1 then multiply by 100 to get a value you can assign to the opacity setting for the lightcell/shadow objects.
Make sure you snap to the grid when placing the objects or it won't look right.