Fenix flashing P2D/L1D/L2D - defect or not?

Hi:

In this thread, moldyoldy and Gunner12 indicated that the flashing while changing modes on Fenix P2D/L1D/L2D was a problem and had been fixed:

https://www.candlepowerforums.com/threads/185772

However, Trevor at Fenixstore states: "I'm afraid that the preflash is a byproduct of the circuit and is present on most fenix lights to some degree. As long as the light is in pristine condition I can issue you a return rma for it."

This wasn't what I had hoped for. I would like a Rebel light that has no flash, then I'd be willing to exchange it, and buy lots more in the future. I will ask Fenixstore if the new L2D.RB100 models flash. If not, I will try to exchange my L1D.RB80 for an L2D.

If they all flash, I will refund it, and send a note to Fenix that they need to get a handle on load step transient response in their driver designs.

This has been talked about and I do believe it is a defect. It is annoying, but not so much so to me that I'd return it. This mentality varies from person to person, but it's still annoying. To me it's more like a scratch on the light when I received it. Since then I've given it more. This also varies from person to person.

Depends on the model / LED and when it was made. My L2D-CE P4 flashes slightly. This is my oldest L2D. My L2D Rebel 100 flashes very blatantly. This was my 2nd L2D. My L2D-CE Q5 does not flash. This is my most recent L2D. I'm not sure I'd consider it a defect, but it clearly can be eliminated.

I have the oldest L2D and there is no flash on that. However, I don't see the flash as a defect and I don't understand why people are so annoyed about it. If it really is a problem, why not just cover the light when you turn it on?

And does the flash occur when you start the light on low? Otherwise, I don't understand the problem at all, since the NV is allready blown stepping down from higher outputs.
But as JamisonM pointed out, it varies from person to person about how annoying they find it.

Lobo said:

And does the flash occur when you start the light on low?

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Yes, it flashes between every mode. Obviously it's most obvious starting on low.

Mine flashes on low, but not between modes.

I've got the L2D100 which is one of the worst offenders due to it's robust flash and high output. It can be like a flashbulb going off when you forget to cover it in a dark environment. I hear the Q5 is supposed to have fixed the problem but I haven't seen one.

Not usually a problem for me since I tend to use Turbo 99% of the time.

My P2D Q5 doesn't flash at all. Maybe they have fixed it ..

The preflash is due to the circuit dropping the power to the LED. In some lights it's longer than others but all have it. The newer lights seem to drop power quicker. When people refer to it being "fixed" this is it. One of them I just handled was so fast I could barely pick it up. But its there. As I mentioned in the email it's a byproduct of the digital regulation boost circuit. Leds like the rebel with lower forward voltage are more sensitive. I've noticed it in non-fenix lights as well.

The p3d will not have this result due to the buck circuit. Xe54- keep an eye out for the rma I'll be sending you this afternoon.

TrevorNasko said:

The preflash is due to the circuit dropping the power to the LED. In some lights it's longer than others but all have it. The newer lights seem to drop power quicker. When people refer to it being "fixed" this is it. One of them I just handled was so fast I could barely pick it up. But its there.

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I recall reading that when they announced the change, not that it was gone, but greatly reduced to the point of not being an issue.

TrevorNasko said:

The preflash is due to the circuit dropping the power to the LED. In some lights it's longer than others but all have it. The newer lights seem to drop power quicker. When people refer to it being "fixed" this is it. One of them I just handled was so fast I could barely pick it up. But its there. As I mentioned in the email it's a byproduct of the digital regulation boost circuit. Leds like the rebel with lower forward voltage are more sensitive. I've noticed it in non-fenix lights as well.

The p3d will not have this result due to the buck circuit. Xe54- keep an eye out for the rma I'll be sending you this afternoon.

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Interesting. Has anyone talked to Fenix about this? If it persists, it makes me more inclined to look for other lights. The Olights don't seem to do it. Though, my Dereelight 3SD modules do. In the Dereelight case, I don't mind as much since I expect to usually use it on high. Plus, the flash is a bit less annoying than on the L1D.RB80.

Obviously, a few milliseconds might slip by without bugging anyone. I'll try to get some scope + photodiode shots of my P2D which seems to not flash at all, vs. the Rebel (before I send it in).

With the Lumileds recall, I think I might be better off switching to a Cree Q5 for now anyway.

Basically, if the flashing is regarded by Fenix as acceptable, then I will be hesitant to buy more of these models in the future. A shame since now I like the UI on P2D better than Olight's memory. If they work on making the flashes go away then I will keep buying lots of Fenixes.

I have a P3D RB100 and I can notice the flash, but barely. Out in the woods with no moon, eyes adjusted to darkness for about 15 to 20 minutes. Switched on to low and it is there under these conditions, but you have to look closely...Very closely. Definitely did not bother my night vision at all, well till I looked straight into it on low. Talk about I see spots

Jarl said:

Mine flashes on low, but not between modes.

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Same thing for my L2D Q5, bought in November 2007 from Fenix-store. The solution is exactly as Lobo says: cover the lens when turning it on. It's only when I forget to do so that I find it mildly irritating. With adjusted night vision, I can easily see the pre-flash through my closed eyelids, but not enough to ruin my night vision.

FrontRanger said:

Same thing for my L2D Q5, bought in November 2007 from Fenix-store. The solution is exactly as Lobo says: cover the lens when turning it on. It's only when I forget to do so that I find it mildly irritating. With adjusted night vision, I can easily see the pre-flash through my closed eyelids, but not enough to ruin my night vision.

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Same here but it's not much of a bother to me. I actually think it's cool, i could see how at pitch black night when trying not t loose night vision it could be annoying.

It makes for an interesting beacon if you keep turning it off and on in Low mode every two or three seconds.

It is not a defect, rather it is part of how the circuit works.
In fact no-one ever mentioned it or even detected it before we had
a run that had a slightly longer flash. That has been resolved and
should not be an issue. Of course if anyone is not happy with theirs
we'd be happy to exchange or refund them within 30 days based on
our return policy.

I really can't see why a microsecond or so of flash is a concern to anyone. I never notice it when actually using the light and can only see it if I look REALLY hard when sitting still, in the dark, while staring at a white wall. I'd think you'd have to be a bit ummm... anal/nerdy/whatever, to let it worry you.
I'm willing to take this back if someone can give me a 'real use' reason why it's a problem and this doesn't include " It ruins your night vision" because that's just cobblers.