My test was done with default settings. Temp sensor seems to be correct within 2°C. No active cooling nor heatsinking of any kind.
TK, thanks for this. I had wrongly assumed Nichia 219c would generate the least heat based on its lowest lumens output. Ideally I like the sustained output as I normally go out at night for 30 minutes walk, and it will be nice to have the light at the same level of output the whole duration of the walk.
What is people’s opinion on what temperature is still considered comfortable enough to hold the flashlight? 50, 55?
ssschen, that’s going to be a subjective thing… you’re going to have to set it at what YOU are comfortable holding. I mod lights virtually daily, machine aluminum and copper on the lathe… my hands are so used to extreme heat that my idea of comfortable to hold is going to be much different than a lot of peoples. Almost like asking what pepper is too hot to eat, depends doesn’t it? 
I understand entirely. But please do humor me / us, at what temperature do you start to consider a flashlight too un-comfortable to hold? 
Around 155ºF. Pretty much have to turn it off and put it on a heat sink at that point. (~68 - 70 C)
50c/55c (120F-130F) is a good temp for me.
I bought more shockli 26650 from rmm last night. Thanks.
My two “early edition” D4S’s.
Making 5685 lumens and 5171 lumens, respectively. Both from Sony VTC5A cells.
For clarification, both of these are made with the MCPCB and Optic that Hank designed/chose for use with the Emisar D4S. Both of these are running Bistro from an FET+1 driver.
Thought I would drop in and share this holster solution for the D4s.
I had an old Olight M21 Warrior holster and it ain`t too bad re-purposed for the D4s.
Depends how long you hold it. Slow burn is a thing. And it’s insidious as you don’t feel it until long after it’s done. There are people who got burns to their legs from using car seat heaters in warm weather. I once burned myself lightly (no damage but skin was sensitive) by holding a warm soup bowl that never actually felt painfully hot. I just held it for a fairly long time.
Okay, in that case it stabilized at a higher output than I would expect. With no cooling or heat sinking, I figured it would settle lower.
During tests I generally have a fan blowing at the light, from 1m away, at the fan’s lowest speed. I’m not sure if this is a good way to simulate the heat-sinking of a hand, but it does at least make a pretty measurable difference compared to stale air. My thermal testing is pretty imprecise though.
It is kinda useful when they do. Otherwise I think they are called flash cubes. (If you know what they are you are really old…)
Know what they are? I probably have some in a desk drawer somewhere. 
I just moved for the second time in 7 years, so I am sure there are none in the box of photography stuff I have hidden in the garage. LOL
This may have already been discussed earlier. But is it possible to mod the light to a different aux led? I don’t love the blue. Would much rather green or even red. Is this doable?
Here’s what the AUX LEDs look like on the meter. This is with the optics and a slight Zircon minus green on top so on the CIE graph the LEDs would actually sit just a bit higher.
Regarding the step-down rate. Keep in mind that if you don’t start on turbo, you should have longer before the light steps down from your initial output levels.
The floor is N clicks, to set it to level N, or 0 clicks to leave the current value unchanged.
The ceiling is 151 - N clicks, so 1 click for 150, 11 clicks for 140, 21 clicks for 130, etc… or 0 to leave the current value unchanged.
The ceiling is basically off by one to make it possible to set the ceiling to turbo.
Are there any good beamshot pictures for this yet?
Do I see what the die/phosfor of the ice-blue aux leds produce or is some of it also the main leds excited by the blue aux leds?