The hotter an incandescent element is, the more efficiently it converts heat to light. Think about how something metal and hot glows dull red, while something

The hotter an incandescent element is, the more efficiently it converts heat to light. Think about how something metal and hot glows dull red, while something metal and really hot glows orange-white. Reaching white-hot is a trade-off, in balance with the limit of the material for how hot you can run the filament, before it boils away.