Factorio Forums

Stacking lamps should increase radius light as showng below:

Red - Current Radius
Green - Ideal Radius

https://imgur.com/a/7jYjUKB

The more lamps are stacked, the more light they produce and increases radius.

Stacking lamps won't increase the illuminated radius (apart from the lamp offset). It will only increase the illumination of the area that's within both lamps' radius.

Because that's how they're currently implemented. Changing them to use inverse square illumination will do as suggested (although require slightly more GPU power).