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The old rating system of “time to 50% brightness” worked 10 years ago, but simply isn’t relevant for today’s flashlights.

That’s because 10 years ago typical flashlight output was 100 lumens. A “high end” light might output 200 or maybe 300 lumens. Battery capacity, not heat, was the limiting factor in sustaining output back then. Those lights were going at max power and output would decline as battery voltage declined.

In 2009, if you had a light that was rated 1 hour to 50% brightness, used it for 1 hour and then turned it on 2 hours later it would start at 50% brightness and decline from there. That rating gave you a good idea of how much battery capacity was left and how many spare batteries you should bring.

In contrast, the limiting factor for today’s flashlights with unsustainable turbo modes is heat, not battery capacity. Today’s lights have thermal sensors and are programmed to intentionally reduce output to prevent injury to your hand.

For example, you can turn on a D4 at max turbo of 4300 lumens. Output will rapidly decline to 50% or less in 20 seconds or so. But if you turn it off and let it cool for 10 minutes, you can then turn it on again and still get 4000+ lumen output. The battery is still almost completely full.

Also, some (but not all) of today’s lights have regulation which can sustain a flat output at an intermediate mode until the cell is almost completely depleted. This is different from lights 10 years which tended to have no regulation.

I like the ANSI system. At least everything is standardized. However, I agree some changes would be helpful. Most useful would be having 3 measurements for each light:

  • Maximum output - the max lumens the light can produce when cool on a fresh cell at turn-on.
  • Turbo mode duration - how long the light can sustain turbo mode until step down to a lower mode, or for lights with gradual rampdowns how long it takes for output to drop to the level of the maximum sustained output.
  • Maximum sustained output - the highest output the light can sustain while tailstanding in a 70 degrees F room.