Explain "stepdown"

michiganstud

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So currently I've chosen to run two primary lights for duty use. I've chosen my 800 lumen Stinger as a car light, bag light, backup.

I've chosen the 1,000 lumen Protac HL-x as my primary belt light for the bat belt. Neither heat up and both have good run times with good light and throw.

I've been hearing about "stepdown" and I looked at the fact sheet for my Protac from Streamlight and the graph shows a significant step-down after 15 minutes! Looks to be almost half ...or from 1000 lumens to about 600 or 700 lumens.

The Stinger goes from 800 to a 600 lumen drop in 30 minutes!!

Why????
 

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xxo

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Time and temperature. After 15 min, you probably won't notice the gradual decline in lumens, but you get more run time and the light won't heat up and burn your hand.
 

bykfixer

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It also helps keep the "lamp" from cooking itself internally.
Ha, it's funny how early on LED's were said to last 100,000 hours. Later 50,000. Now some say 30,000. It causes me to wonder if that's because of all the heat from chemial reaction(s) as things get brighter.
Btw that's still 1264 days.
 

Olumin

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Yeah, a lot of LEDs are overdriven these days. They'd probably still last 100,000 hours if they weren't, but manufactures push emitters to their maximum to get the highest output they can print on the box. LEDs are especially efficient at low current with efficiency decreasing the higher you push them.
 
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3_gun

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Marketing.

A 1000L light is easier to sell than a 500L light in todays market. The reason is the FL1 standard & how it's written & how the company choose to meet it. Run time = lumen output at 30sec to a level equal to 10% of that number. That at 30sec level is supposed to be the level claimed as the lights max, but 500 doesn't sell as well as 1000. So what they do is ignore that or play with a time or temp setting to get the first 30sec to be a marketing level instead of a useful run time.

The next choice is how they handle the "step down"of the light. ALL LIGHTS WILL STEP DOWN! The question becomes how fast & how. Some will step down to a level that the driver can hold for HOURS & them step down to the next lower level until they reach a low or moonlight mode. Then LVP will turn the light off to protect the battery. Others let the light dim over time based of voltage levels OR by the temperature of the light. Using voltage means the lights dims slow until the LVP kicks in.(if the light has LVP) Many lights that use non rechargeable batteries don't need or use LVP as they are single use cells. Lights w/temp control dim based on a max temp that the light can be safely run at & will vary based on the "room" temp & other cooling factors.(wind, rain, on/off cycles by the user)

FL1 tests at 70F with the standard cell suggested by the builder. Again their testing is to 10% of the 30 sec lumen level. So if the maker wants to use a big step down; 500 to 100 they can market a crazy long run time w/o telling you that you'll end up with about 5 minutes warning that the light is about to shutoff. That is done by programing & not controlled be voltage or temp. Lights controlled by those will vary wildly based on environment & how the user uses the light.

Cold, windy, wet Fall day, the light might hold full out put for an hour w/no step down before you find yourself in the dark because of LVP kicking in. Or if you use the light in short bursts you may never notice/see a step down until you can't use high or turbo from off anymore; take the hint & change batteries.

Lots of factors go into run times so you need to know if your light uses; none, LVP, temp, programming or a mix of these to protect the light & how your planned use is affected by it.

I find myself taking about 40-50% of the lights claimed lumens, see if they have a level equal to or near that, & then figure what 50-60% of the claimed run time is at that level to judge if it's enough for my use.

Third party testing that doesn't use FL1 standards can often give you better insight into how the light will really work. Still ITRW having two or more lights on hand is a must in critical use areas as so many variables go into what really happens THAT DAY
 
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Thetasigma

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No such thing as a free lunch. If you want constant runtime at a given level, you want somewhere in the ballpark of 200-500 lumens with a modern emitter and a decent size host, 18650 or so much should do the trick. If you want a smaller host and/or more lumens, at some point you will have to step down the light to prevent damage to the light or the user due to heat. A constant runtime level can be increased by going with a larger host, more surface area, active cooling l, etc, but quickly becomes unwieldy and impractical. A pocket size LED light will never do 1000 lumens continuously, there isn't enough efficiency left in the technology to gain to reach a low enough level of heat generation to make it possible.

3_gun's point on marketing is excellent as well and factors into the engineering decisions made as far as design, output, and program behavior are concerned
 

idleprocess

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I've been hearing about "stepdown" and I looked at the fact sheet for my Protac from Streamlight and the graph shows a significant step-down after 15 minutes! Looks to be almost half ...or from 1000 lumens to about 600 or 700 lumens.

The Stinger goes from 800 to a 600 lumen drop in 30 minutes!!
Due to the logarithmic nature of brightness perception, you will have difficulty discerning 1000lm from ~650lm and even greater trouble telling 800lm from 600lm.

Personally I have two of the same general model of flashlight with different drivers and different 4000K LEDs in them. On paper one is about twice as bright as the other. But without unusually close scrutiny of the same scenes that I have illuminated literally hundreds of times walking the dogs the main difference seems to be the markedly different white balance of the significantly different LEDs; A/B testing makes it a bit more apparent but the difference is subtle.

Ha, it's funny how early on LED's were said to last 100,000 hours. Later 50,000. Now some say 30,000.
I recall 100,000 hours originating from low-power indicator lamps generally driven well below the typical 20mA maximum current. The subsequent downrates were likely hard-won experience as LED packages started dissipating entire watts.

A 1000L light is easier to sell than a 500L light in todays market. The reason is the FL1 standard & how it's written & how the company choose to meet it. Run time = lumen output at 30sec to a level equal to 10% of that number. That at 30sec level is supposed to be the level claimed as the lights max, but 500 doesn't sell as well as 1000. So what they do is ignore that or play with a time or temp setting to get the first 30sec to be a marketing level instead of a useful run time.
Not unlike daily driver cars and their 0-60 / 0-100 times, top speeds, peak torque values, maximum tow ratings, ground clearance, etc. Sure someone has tracked, towed with, offroaded just about everything, but - like peak lumen / cd ratings - those are corner cases the typical daily driver will not realize many times in its lifespan.

I'm OK with peak lumen ratings and the invariable physics of small lights outrunning their thermals, however I do wish that honest runtime graphs were similarly ubiquitous so I could make more informed decisions.

A constant runtime level can be increased by going with a larger host, more surface area, active cooling l, etc, but quickly becomes unwieldy and impractical. A pocket size LED light will never do 1000 lumens continuously, there isn't enough efficiency left in the technology to gain to reach a low enough level of heat generation to make it possible.
The fundamental problem with the kind of peak output we see claimed on EDC sized flashlights is the total lack of physical space, mass, and power budget to keep them at comfortable temperatures to sustain that value. Even the larger multicell >10k lm class lights we see with active cooling struggle to maintain output, such are the demands of cooling and lack of power/space budget for anything with a compressor / refrigerant.
 
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bykfixer

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In side by side use I can hardly tell the difference between my 320 lumen SureFire G2x Pro and 650 lumen Elzetta Bones in dark conditions.

Now busting up shadows in a light polluted situation that extra 325 lumens does show up. Say I pull a manhole top at mid day on a sunny day, from a standing position shine the 325 lumen light into the dark hole and see darkness. The 650 lumen light shows me it's 10 feet deep and full of leaves. But that's why I carry a 1000 lumen Maglite ML150 in my work truck along with those other two. It handles all that heat by stepping down a bit to the level of the 650 lumen light.
 

aznsx

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You're getting some OK responses, although some are a little short. It's about way more than "marketing", Sir. The biggest problem is that many people aren't aware of exactly what they're buying, because unlike Streamlight, not all manufacturers put in on a graph for you. That's their choice if they'd rather you not know. (yeah, I could be talkin' 'bout you, SF).

SL could sell you a light that comes on at "6-700 L" and runs there dead flat. Instead of that, they design it so if you set it for 'max', it can crank out ~1K for a good 30 seconds first, then taper gradually down to 6-700 so it doesn't self destruct.

I think you're a LEO, so I'll just ask you: When you step out of the vehicle (/etc.) and draw that light and push the 'go' button, often needing all the light you can get for a short period, would you rather have the 6-700 during that initial period, or the 1000?

I'm not a LEO, but I can tell you which I want, and it's not "marketing". If I have the light set to 'max', I want all the light I can get during that initial period. 30 seconds can be forever when things are going South. However, I don't want to speak for you. Which would you prefer Sir?

I like to know what I'm getting, so I prefer to do business with businesses who want me to know what I'm getting. Just to give you another example, to look at, here are some graphs provided for one of my more recent purchases (Elzetta Alpha).

Alpha_Gen3_Runtime_Graph_1000x646.png
Alpha_Gen3_Runtime_small_scale.jpeg
 

KITROBASKIN

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Additional factors perhaps not discussed in previous posts.
When energized, emitter gets hotter and efficiency goes down, even if you can't feel heat on the exterior of the flashlight. Battery will also sag under sustained load.

One of the great things about flashlights is that they are not so expensive a person can try different types. All the graphs and ad copy in the world will still not tell you if one flashlight best meets your needs.

Reading CPF can also inform to a certain degree, but also mislead at times.
 

michiganstud

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Soo......would it be safe to say that the Surefire 6Px LED that is rated at 600 lumens will have a step down ...probably to 400-ish? Or is it safe to say that the lower lumen model lights stay constant longer?

Which is going to run more true? The 1000 lumen Protac or the 600 lumen 6Px?
 

Dave D

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Soo......would it be safe to say that the Surefire 6Px LED that is rated at 600 lumens will have a step down ...probably to 400-ish? Or is it safe to say that the lower lumen model lights stay constant longer?

Which is going to run more true? The 1000 lumen Protac or the 600 lumen 6Px?
Good question and well presented, I don't know if the answer to that one is out here.

Which is why I recommend the Malkoff M91T MD3 or MD4 to LEO's, it comes on momentarily at 900 lumens and then constantly runs at 750 lumens, it has a TIR lens which throws well but it still has good spill. My M91T MD3 will run for 1 hour 30 minutes on two 18500 2300mAh batteries, the MD4 with two 18650 3600mAh batteries should give closer to two hours runtime. It won't throw quite as far as the Stinger HL 800 lumen model but it's very close and a much smaller package that will take up little belt space. The M91T can have the high/low option so always come on in high mode when the head is tight, loosen a fraction for low mode. Another benefit is there is no strobe! Malkoff do an LEO discount.
 

desert.snake

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Soo......would it be safe to say that the Surefire 6Px LED that is rated at 600 lumens will have a step down ...probably to 400-ish? Or is it safe to say that the lower lumen model lights stay constant longer?

Which is going to run more true? The 1000 lumen Protac or the 600 lumen 6Px?
I don't see a step down, maybe just battery drain. Need more tests


surefire-6px-runtime-png.png
 
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bykfixer

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Again, in terms of the 6" 6 volt light that 500-650 lumen output was a sort of sweet spot where heat disippation through well engineered conductivity could mean a pretty steady output. Yet as the LED gets warmer some drop off would occur due to physics not a purposeful stepdown. Soon after the battery would run out of fuel.

If members here think back, it was when companies were touting 700, 800, 1000 oh my goodness we've reached a thousand using a special high drain battery nonsense popped up suddenly there was fine print saying "for 44 seconds then stepping down to 75% output" which was actually around 500-650.....
 

aznsx

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Soo......would it be safe to say that the Surefire 6Px LED that is rated at 600 lumens will have a step down ...probably to 400-ish? Or is it safe to say that the lower lumen model lights stay constant longer?

Which is going to run more true? The 1000 lumen Protac or the 600 lumen 6Px?

Please correct me if I'm wrong, but when I look that light up on the SF site, it is billed / advertised / specified as a 2xCR123 light, so it is built to run on ~6V.

When I look at the test / review where the graph desert.snake provided was obtained, I read:
look at this decent runtime. I only used 2500mAh 16650 for the test and it turned out quite impressive.
I don't have any 16650 cells, but I would assume they are 3.7-4.2 V cells. I wouldn't draw any significant conclusions when comparing the performance indicated in that test with other data we normally reference which is either provided by a manufacturer (who always test using provided / recommended / specified power supply per ANSI FL-1), or third party tester who conforms to that convention. Effectively 'apples and oranges'.

EDIT: You could always contact SF and request a copy of their output graph. I assure you it exists.
 

aznsx

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BTW @michiganstud , here's a thought. Since you're exploring the subject of output levels and how they are 'managed' by various manufacturers with respect to the % of initial max output, and also other lower outputs and how they are / are not maintained over time, this might help you develop a 'feel' for that. I'm not commenting subjectively otherwise on this particular manufacturer, and many of their lights now sport gigalumen 'max' outputs so one must consider that, but Fenix is one of the few manufacturers who publish output / time graphs for many of their lights which plot not only the output at 'max' setting, but also most / all of the other selectable output settings as well - all on one graph. You can pull up those graphs (which they may actually put on their product packaging - not sure), at a site like 'fenixlighting'. While it may not be models you're specifically interested in, it will provide some additional data points for you to consider that might help you develop a 'gut feel' for how these things are (perhaps) typically implemented, and what you might expect from other products out there. Few (if any?) other manufacturers publish output graphs for all / most of their lights' multiple output levels other than Fenix (AKAIK) - and that is to their credit, it must be said. They're also a PLATO member company, so while they may play a few games with their marketing, their data can probably be assumed to be fairly 'legit'.

EDIT: Again though, there simply IS no substitute for specific manufacturer-supplied data on the lights you're interested in.
 
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