Why so much interest in hand-held flashlights relative to headlamps?

[Bolster]

A brighter headlamp is also less efficent on lower levels most of the time, like zebralight.

Really?!? Wow I did not know that. I thought the brighter they were at the top end, the more efficient they were at the mid and lower levels. Not true?

 

[gcbryan]

Really?!? Wow I did not know that. I thought the brighter they were at the top end, the more efficient they were at the mid and lower levels. Not true?

I don't think the XM-L is more efficient on lower settings than the XP-G on similar lower settings. So it depends on the led. The SST-50 and 90 leds aren't as efficient as the newer Cree leds in general.

Any led is more efficient of course at a lower setting than it is on a higher setting.

 

[uk_caver]

When it comes to overall packages, I guess a lot depends on the type and design of the driver.
Some drivers might by definition be less efficient at lower power levels (such as constant-current drivers running off 3xAA/3xAAA) due to having to waste more voltage headroom.
That said, we still look at LED output in terms of lumens/mA, and if I drive an LED at constant current from a 3-cell pack, even though the driver is less efficient at lower power since it's 'wasting' more voltage, at higher powers that 'wasted' voltage just shifts to the LED as the Vf increases, and I'm still going to get at least as many mAh out of the pack at a low drive than a high one, and at least as many lumens per mA at a low setting as a high one. As long as I don't have meaningful overheads in terms of the driver-controller's own power consumption, lower settings would be more efficient overall.

Some drivers might improve efficiency at lower power levels - I'm sure that some of the cheap boost drivers I tested were more efficient at reduced power.

Though I guess ultimately, runtime is what matters - if someone isn't going to make it through the night running at high power, whether medium power is slightly more or less efficient is secondary to the fact that medium power will have a rather longer runtime.

Come daylight, if someone is running rechargeable cells, as long as they didn't run out of power altogether, they can just get charged up again.
If someone was running alkalines, their increasing loss of effective capacity at higher drains is likely to be far more important than any marginal efficiency differences between power levels.