Preflash explanations

I recently got my hands on a 4Sevens Quark AA2 Tactical, which has two distinct programmed modes that it will remember. I am noticing a very distinct pre-flash when I turn on the light in the lower modes, especially moonlight mode. I called 4Sevens and spoke with someone that explained that the pre-flash is required in order to maintain efficiency and some other mumbo jumbo about the speed of light.

I'm no electrical engineer, but if you have a device with a memory that knows what mode it will be entering before the user turns it on, why in the world would you need to engage the device on full blast before switching to the correct mode? That just makes no logical sense to me. The explanations I have heard just sound like an excuse for a deficient design, so many programmed devices out in the world seem to do just fine turning themselves on in the correct mode to begin with.

Am I way off base here, or do many people give merit to the explanations given for why pre-flash exists?

salimoneus said:

II called 4Sevens and spoke with someone that explained that the pre-flash is required in order to maintain efficiency and some other mumbo jumbo about the speed of light.

Click to expand...

LOL. And this is yet another reason why 4sevens will never get another cent of my money. Although no other light (that I am aware of) exhibits this annoying and unecessary trait, 4sevens has made no effort to correct the issue for years and instead try to say it is a deliberate part of the design and intended function.

FAIL.

Their circuit design requires that efficiency at low levels and the part that would reduce preflash be inverse. In other words, to get their efficient low levels, you'll get a pulse of brighter light. To eliminate that would drastically cut low-level runtime. Why don't you palm the bezel or press it against your leg the first time you activate it? There is variation in how severe the flash is - my light only does it when it was on a higher setting the last time it came on.

Also this has been discussed in www.candlepowerforums.com&hl=en&prmd=imvns&ei=bLVGT9TFAaW80AGp6YyjCg&start=10&sa=N&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=94ee7be95c55ec77&biw=999&bih=555]dozens (hundreds?) of threads.[/url]

Well-documented characteristic, if you don't like it don't buy it.

AnAppleSnail said:

Their circuit design requires that efficiency at low levels and the part that would reduce preflash be inverse. In other words, to get their efficient low levels, you'll get a pulse of brighter light. To eliminate that would drastically cut low-level runtime. Why don't you palm the bezel or press it against your leg the first time you activate it? There is variation in how severe the flash is - my light only does it when it was on a higher setting the last time it came on.

Also this has been discussed in www.candlepowerforums.com&hl=en&prmd=imvns&ei=bLVGT9TFAaW80AGp6YyjCg&start=10&sa=N&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=94ee7be95c55ec77&biw=999&bih=555]dozens (hundreds?) of threads.[/url]

Well-documented characteristic, if you don't like it don't buy it.

Click to expand...

One of the big reasons I prefer the lights with tail engagement button and a momentary on, is because many times I am operating the unit one handed. I also want my source of light to immediately be on target where I need it, not pointed in some useless direction, which will then require me to make another motion to put the light on target. That just makes no sense to me and why should I have to go through some silly routine because of an apparent design defect?

Why specifically would it "drastically cut low-level runtime"? What exactly in the circuitry would cause that, do you know, or is this just what was claimed by the manufacturer? I'm notorious for not believing everything I hear or read. Funny how that usually works out to my benefit.

Finally, are you saying this is a 4Sevens-specific issue, or does it apply to all multi-mode LED flashlight manufacturers regardless of their design?

So every other flashlight that offers low-level operating modes must exhibit the same pre-flash, and if they don't then their lights won't be nearly as efficient as 4Sevens?

salimoneus said:

One of the big reasons I prefer the lights with tail engagement button and a momentary on, is because many times I am operating the unit one handed. I also want my source of light to immediately be on target where I need it, not pointed in some useless direction, which will then require me to make another motion to put the light on target. That just makes no sense to me and why should I have to go through some silly routine because of an apparent design defect?

Why specifically would it "drastically cut low-level runtime"? What exactly in the circuitry would cause that, do you know, or is this just what was claimed by the manufacturer? I'm notorious for not believing everything I hear or read. Funny how that usually works out to my benefit.

Finally, are you saying this is a 4Sevens-specific issue, or does it apply to all multi-mode LED flashlight manufacturers regardless of their design?

So every other flashlight that offers low-level operating modes must exhibit the same pre-flash, and if they don't then their lights won't be neraly as efficient as 4Sevens?

Click to expand...

Feel free to disregard what I write - Words on the internet are free, giving them no value

Please read my post. "Their circuit design ..." [has these characteristics]. Which preflash do you mean? Where the first activation at low levels starts at the previous brightness level, or the lesser one where the moonlight mode can blink more brightly if it sits idle for minutes? That first is because of a resistor value on the circuit board. Feel free to replace yours with a smaller SMD resistor to remove that problem. This discharges the circuit more quickly, increasing parasitic drain and decreasing the duration and intensity of this flash effect. The other, I don't know about.

The only lights I know of that have similar dimness are HDS lights. I've got one on order, so I'll let you know how it is.

I'm a software engineer not a hardware engineer, but I know that every single design of anything has to make (usually painful) compromises. It seems reasonable to assume that the the pre-flash is the price this particular design paid for efficiency. It also seems reasonable to assume that there might be other designs out there that could keep the same efficiency without having the pre-flash as a side-effect. But again, I'm speculating.

As a customer you look at the feature-set and apply it to your own wants and desires. That goes for any customer and any product. To me, the good products are simply the ones with a big overlap between what I want and what is provided.

For me personally as a customer and enthusiast of moonlight modes, the pre-flash is not worth whatever the gain in efficiency, which I'm stil not convinced is huge. It's a complete deal-breaker. That's why I go with the Thrunites for moonlight mode. I would be open to maybe something like an SC51 but you have to guess that .6 of a second and if you guess wrong instead of a moonlight mode you get full blast, which again, goes against what I personally look for in a moonlight mode light. But that's technically not pre-flash, right? And the SC51 is supposed to be one of the most efficient you can buy. So it seems like there are designs possible that keep the same efficiency without pre-flash.

But either way, I understand for many, the pre-flash would be a small price to pay for the extra run-time.

So in my probably ignorant and wildly-speculative opinion, there just aren't many companies that build what I would call a good moonlight mode light. I want to be able to activate my moonlight mode flashlight with a 100% chance that I will get only moonlight.

Others have different wants/needs and I respect that too. And it hasn't been all rainbows and puppy dogs with my Thrunites either. I've had some issues with them. But at least I've never had a pre-flash

The preflash does not bother me if I stop looking for it. I would much rather have long battery life. Yes it is there but it is so minor that if you forget about it you will not see it.

AnAppleSnail said:

Well-documented characteristic, if you don't like it don't buy it.

Click to expand...

Or return it, which is what I did. To me it is the biggest flaw of the Quark series and they have done nothing to fix it. And while all you have to do is search for Quark and preflash and see a lot of threads about this, you don't read much about it otherwise.

I guess I just don't understand why this is a challenging problem to solve. We have space shuttles flying missions for decades, and can clone human beings, but we can't engineer a simple affordable lighting device that starts up and provides the proper amount of energy to an LED in order to put it in the correct brightness without strobing out the user with a flash at maximum intensity? This just boggles my mind. Is this really that difficult? Is this a common issue with most manufacturers today with comparable model flashlights?

I'm not really convinced that a pre-flash is necessary in order to attain good efficiency. Maybe it is in 4Seven's current design, but not in general.

I have both a Quark single AA tactical and AAx2 Tactical with the XPG emitters and they both have pre-flash. This is a problem when trying to move about without waking people or being noticed.

I also have a QuarkX AAx2 tactical with the neutral XML emitter. This has no pre-flash at all. Whether this is a new circuit design or something that the XML itself eliminates I'm not sure.

Just like any other manufacturer, 4/7s has it issues and faults. You make your choices and live everything else it comes with. My Quark AA has moonlight pre-flash, loose threads, a greenish tint, and bit too wide battery tube. But for this moonlight fanatic, all those imperfections are but a mouse fart in comparison to being able to pull 250/450 hours (Eneloop/Alkaline) from a single AA batt. with enough light to do pretty much anything I need to with just a bit more work aiming the hot spot for certain tasks (like reading).

Zebralight 51s also have a 300+ hour moonlight, no pre-flash, but it's PWM at that level. ThruNite has a moonlight, I assume no pre-flash, but at half the Lumens AND less than half the runtime. Similar with Jetbeam's RRT. All have much shorter warranties. HDS has a very efficient moonlight, and the best warranty, but no AAs and higher price. You make your choices - nothing's perfect.

Personally, I don't even see my pre-flash because I always like to start my lights pointing at the ground and then draw the light up to my subject (about 0.5 sec.). No matter what mode you're starting up, it's always easier on the eyes to bring light into view in a reflected>spill>hot spot sequence. And of course, if you selected the wrong mode, it's easy to catch before blasting yourself.

Just my $0.02

I don't think I've seen the pre-flash on my Quark AA for at least a year. It's still there, I'm sure, but I turn it on and set the level I want before I pull it out of the holster.

--flatline

I call BS on the need for preflash in order to keep the circuit efficient in their circuit design. If that were the case the preflash would be constant. However, my light exhibits the preflash only once and awhile with no rhyme or reason. Again, if it were a part of the design, the preflash would be constant.

duro said:

I call BS on the need for preflash in order to keep the circuit efficient in their circuit design.

Click to expand...

Correct. But it is cheaper to manufacture lights without the extra circuitry to prevent/eliminate it. And people still keep believing the hype that it is a necessary "design feature".

On a side note, I personally think that the supposed "benefit" of having 300+ hours of runtime is a bit overstated in this day and age of high quality rechargeable and lithium batteries. What is that like 12 consecutive days of usage? Seriously how many people are not going to have the opportunity to change batteries within that time period? There is always a point of diminishing returns. Don't get me wrong, of course having a longer runtime is preferred, but not if you're going to get a random blast of max brightness, and need to turn the light on in some funky way to hide the flash as a consequence. I guess some people are willing to put up with it for that extra 100 hours of moonlight or whatever, but to me it just seems like a fundamental design defect.

reppans said:

Zebralight 51s also have a 300+ hour moonlight, no pre-flash, but it's PWM at that level.

Click to expand...

Ahh, I didn't catch that from Selfbuilt's review the first time through. Thanks for pointing that out.

Really, what I want is:

- Current controlled moonlight mode - as low as possible.

- No pre-flash.

- Common format like AA / AAA for road trips and far away from home.

- As long of a run time as possible.

Racer said:

Ahh, I didn't catch that from Selfbuilt's review the first time through. Thanks for pointing that out.

Really, what I want is:

- Current controlled moonlight mode - as low as possible.

- No pre-flash.

- Common format like AA / AAA for road trips and far away from home.

- As long of a run time as possible.

Click to expand...

Well, if you can live with QTC (different set of issues), you could get a Peak - moonlight, efficient, long run-times, no pre-flash, and whatever battery format you like

archimedes said:

Well, if you can live with QTC (different set of issues), you could get a Peak - moonlight, efficient, long run-times, no pre-flash, and whatever battery format you like

Click to expand...

Yep, I've been reading those threads today. And the routine maintenance is something that wouldn't be a problem. That might just be what I'm looking for.

Does the QTC material ever have to be changed, or just cleaned?

the older Quarks did have pre-flash, the reason being is that the circuit needs an influx of voltage before its memory kicks in and "remembers" the setting it was left on (esp in the lower modes). This circuit was probably improved in the XML lights they newly offered. I'll bet the improved the response time of the circuit to avoid the surge of voltage which causes the pre-flash.

Anyway, if you are a Quark owner who knows your light has pre-flash, hold the bezel or cover it with your hand before switching the light on, this should prevent ruining your night vision or alerting anybody to your location due to the bright flash before going into moonlight mode.

Not really a deal-breaker if you ask me. In fact, if you get their newer lights (xml line) these preflashes are no longer present.

Why hasn't a mod stepped in yet? The first light I bought was a Quark Turbo 123x2 and it had preflash. I had spent 80 bucks on it and was pissed it kept flashing me. To sum up your frustration. Yes, it sucks, and their excuse is not great. However, every manufacturer has its trade offs and caveats. I have a Quark XML AAx2 Neutral and it does not exhibit preflash. Its xml based, and has half the runtimes but twice the output. I put it on an AA body with a 14500 and the thing screams. No preflash. Regular model. Sell yours on the market and get one with a regular interface. All the benefits of a Quark without the preflash.