Affect Normal Fires

This spell enables the magic-user to cause small fires—from as small as a torch or lantern to as large as a normal bonfire of 3 ft. maximum diameter—to reduce in size and light to become match-like or increase in light so as to become as bright as a light spell. 

Reducing the fire will cut fuel consumption to half normal, and increasing the fire will double consumption. 

Note that heat output is not altered in either case.