system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how do lumens work? How much brighter is one 800 lumen bulb than two 400 lumen bulbs?
gpt
Lumens are like watts, but weighted to only include the light we can see; infrared and below is out, as is ultraviolet and above. So a bulb with twice as many lumens is twice as powerful, as far as we can see. The trick is that the human eye has roughly logarithmic sensitivity. If you saw a row of bulbs which were 100, 200, 400, 800 lumens, i.e., going up in brightness exponentially, you’d say their brightness was stepping up evenly.  If you instead saw bulbs at 200, 400, 600, 800, you would think that there wasn’t much difference between the two brightest.