LD10 and LD20 same brightness?

Is it normal for the Fenix LD10 and LD20 (both R4) to appear to be the exact same brightness in all modes including turbo? In other words, is the 73 lumen difference too small for the eye to perceive? I have both of these lights running on freshly charged Eneloops, and if I shine them at a wall 10 feet away, I wouldn't be able to tell which was which based on the beam. The beams literally look exactly the same.

If it helps, the LD10 is drawing 2.76 watts on turbo (2.3A @ 1.2V) and the LD20 is drawing 3 watts (1.25A @ 2.4V). I see three possibilities: (a) both lights are putting out rated lumens, but the eye can't tell the difference, (b) the LD10 is able to pull enough power from the Eneloop to put out more than 132 lumens, or (c) the LD20 is defective and is putting out less than 205 lumens. Only (c) would be a problem for me.

Anyone with both of these lights who can share their own experiences?

You're not comparing the output by comparing the beams. You're mixing up lumens and lux. The LD10/20 Q5 has a smaller, brighter hotspot than the LD10/20 R4 models, and thus appears brighter/as bright.

If you really want to compare outputs, do a ceiling bounce test. Basically, go into a dark room. Turn on one light, and point it at the ceiling. Turn it off and repeat with the other light. As you do, look around the room to see which one illuminates the room better. The one that does has the higher output.


Incidentally, there has been some controversy as to whether or not the new R4 models are rated at out the front lumens or not. The old Q5's were LED lumens, but it's such a small loss anyway that you won't really notice.

John_Galt said:

You're not comparing the output by comparing the beams. You're mixing up lumens and lux. The LD10/20 Q5 has a smaller, brighter hotspot than the LD10/20 R4 models, and thus appears brighter/as bright.

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Just to be clear, the two lights I'm talking about are an LD10 R4 and an LD20 R4. There are no Q5 emitters involved. That's why I found it so odd that the beams looked identically bright (which doesn't seem right), as well as having the exact same shape and pattern (which I would expect).

Thanks for the tip about the ceiling bounce test. I'd say it was pretty inconclusive; both lights seemed to provide the same amount of illumination. I'll try in a bigger room when I can, since that might give a more definitive result.

"You're not comparing the output by comparing the beams. You're mixing up lumens and lux. The LD10/20 Q5 has a smaller, brighter hotspot than the LD10/20 R4 models, and thus appears brighter/as bright."

"Is it normal for the Fenix LD10 and LD20 (both R4)."

John, lumenguy has both R4 models.

The difference between these two lights on high&turbo is not noticeable unless you have very good eyesight, and you are comparing the beams outside at long range.

An easier way would be to set a camera on the lowest possible exposure and take two shots of the different lights. (then compare)

lumenguy said:

Is it normal for the Fenix LD10 and LD20 (both R4) to appear to be the exact same brightness in all modes including turbo?

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EDIT - sorry I misread the above post.

It is completely normal for all modes to be the same EXCEPT on turbo. It has been this way since the very first L1D/L2D/P2D series (and subsequent LD10/L20/PD20 iterations).

The reason for this is that all 3 lights use exactly the same head - they are all identical, thus have identical output levels. The practical difference is that the LD20/PD20 are roughly twice as bright on Turbo than Hi, whereas the LD10 (until recently) was unable to produce much beyond the Hi mode on standard cells.

What's changed on the new R4 models is the lower modes are lower in output, so there is now a difference between Hi and Turbo on all models.
On earlier lights, you were not likely to be able to discern a difference between Turbo and Hi on the LD10. In my experience of every model from the original Cree P4 to the Q5, the gain on Turbo was usually only ~1-3% more output. It is is now noticeable on the R4 models, because Hi is lower.

Again, at the lower outputs, you will not see a difference between the members of this family (the PD30 is different, since it uses a different circuit to support higher voltage). The LD20 should be brighter than the LD10 on Turbo, though.

I only have the Q5 version and can see a definite difference.

The modes are the same EXCEPT for turbo.

Leave the LD10 on high and twist to turbo, observe the change in throw/cieling bounce.
Do the same with the LD20 (in my case LD10 with L2D tube)
The LD10 is hardy different from high to turbo, you really need to look carefully, the LD20 is easy to spot.

Use one of the heads and swap the tubes. Maybe you got a particularly bright LD10 and dim LD20 in the LED lottery.

Go outside and you should see a difference in turbo, just pointing at a wall at 10' is most of the time useless. Next best thing besides outside is as mentioned already and do a ceiling bounce.

lumenguy said:

Just to be clear, the two lights I'm talking about are an LD10 R4 and an LD20 R4. There are no Q5 emitters involved. That's why I found it so odd that the beams looked identically bright (which doesn't seem right), as well as having the exact same shape and pattern (which I would expect).

Thanks for the tip about the ceiling bounce test. I'd say it was pretty inconclusive; both lights seemed to provide the same amount of illumination. I'll try in a bigger room when I can, since that might give a more definitive result.

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Ah, I misread you post. My apologies.

Either my eyes are playing tricks on me, or these two flashlights really are putting out the same amount of light. Even outside, the intensity and throw distance seem to be virtually identical. I even tried swapping heads, and got the same results. I definitely notice the difference between high and turbo, both on the LD10 and LD20. I would say that it's a noticeable difference that anyone would be able to spot. Even the spill gets noticeably brighter when going from high to turbo, both on the LD10 and LD20. I don't understand why it's like this, but both lights are bright enough for their intended applications, so I guess it's not worth worrying about. If anyone else has both the LD10 R4 and LD20 R4, I would still be curious to hear how they look side-by-side and if you are seeing the same thing that I am.

lumenguy said:

Either my eyes are playing tricks on me, or these two flashlights really are putting out the same amount of light. Even outside, the intensity and throw distance seem to be virtually identical. I even tried swapping heads, and got the same results. I definitely notice the difference between high and turbo, both on the LD10 and LD20. I would say that it's a noticeable difference that anyone would be able to spot. Even the spill gets noticeably brighter when going from high to turbo, both on the LD10 and LD20. I don't understand why it's like this, but both lights are bright enough for their intended applications, so I guess it's not worth worrying about. If anyone else has both the LD10 R4 and LD20 R4, I would still be curious to hear how they look side-by-side and if you are seeing the same thing that I am.

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Sorry, just double-checked and amended my earlier post.

The newer LDx0 series have slightly lower outputs in Hi than previous generations of the LxD/early LDx0 series. This means that even on the LD10, you will see a difference between Hi and Turbo now (i.e. 105 lumens to 132 lumens, according to specs).

But you should definitely see a greater difference compared to the LD20 when going from Hi to Turbo (i.e. 105 lumens to 205 lumens, according to specs).

The difference between 132 and 205 lumens should be noticeable by eye, given the beam patterns are the same.

The Eneloops and alkaline batteries have different voltages. Try the experiment with fresh new 1.6 volt alkaline batteries and the difference may be evident.

aehaas

This just keeps getting weirder. With alkalines in the LD10 and LD20, the turbo brightness still looks the same for both. But the LD20 loses low mode when running on alkalines. Low is the same as medium. I know that happens with lithiums, but these are basic store-brand alkalines. I might send this LD20 back, since I don't think it's supposed to lose low when running on alkalines. Maybe there is something wrong with the driver.

The LD20 R4 does lose low on alkalines. Mine does this too. I do not have an LD10 R4 to compare it with though.

lumenguy said:

Either my eyes are playing tricks on me, or these two flashlights really are putting out the same amount of light.

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As luck would have it, I have just received a pair of LD10-R4 and LD20-R4 lights to review.

I can tell you right now that you are NOT crazy. I too was surprised to see that on initial activation, the LD10 and LD20 are indeed putting out a similar amount of light on Turbo on Eneloops and alkalines. oo:

However, on NiMH, the LD10 quickly drops off to a regulated level that is intermediate to the initial output on Turbo and Hi. Thus, the Fenix specs may actually be reasonable - but you have to wait ~5 mins on LD10 until it levels off. All the other modes are regulated on alakline/NiMH.

My preliminary results tell me that overall output/runtime efficiency is right where I would expect it, for both models. Might take me a week or two to get the full review up, but it doesn't to me so far like there is anything wrong with your lights.

:wave:

selfbuilt said:

As luck would have it, I have just received a pair of LD10-R4 and LD20-R4 lights to review.

I can tell you right now that you are NOT crazy. I too was surprised to see that on initial activation, the LD10 and LD20 are indeed putting out a similar amount of light on Turbo on Eneloops and alkalines. oo:

However, on NiMH, the LD10 quickly drops off to a regulated level that is intermediate to the initial output on Turbo and Hi. Thus, the Fenix specs may actually be reasonable - but you have to wait ~5 mins on LD10 until it levels off. All the other modes are regulated on alakline/NiMH.

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Thanks for proving that I'm not crazy! That's what I get for not being patient enough when doing my tests.

Maybe this just is further proof of how you really cannot tell the difference between lumens with the naked eye and thus how lumens ratings really shouldn't be taken *too* seriously.

This week will arrive me my LD10 and I will do a test to see how do they behave a together one to the other, perhaps using the two in the helmet of my bicycle. It thought to do my comments on them, but you won me.

In any case, my LD20 gives a powerful and constant beam of light that lasts 1:40 hours with NiMh of 3000 mAh before vanishing. And the Turbo mode is amazing.

Yes, the two models give me the same brightness. I would not be able to note the difference between the LD20 and LD10. In this page a guy says Fenix LD-10 R4 can output 176 OTF lumens:

http://www.light-reviews.com/fenix_ld10_r4/

A marvelous discovery for me.

The BIG difference between LD10 and LD20 is the battery life. In LD20 with 3000 mAh NiMh the runtime is 1:35-1:40 hours. In LD10 is 45 minutes. Both in Turbo mode. However, for me is a very good runtime. In the lower modes probably be a lot greater.

We live in a wonderful era of great flashlights.

Teobaldo said:

We live in a wonderful era of great flashlights.

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I totally agree. I've been EDCing my LD20 since I received it as a Christmas gift last year and I absolutely love it! I have zero regrets.

Teobaldo said:

Yes, the two models give me the same brightness. I would not be able to note the difference between the LD20 and LD10. In this page a guy says Fenix LD-10 R4 can output 176 OTF lumens:

http://www.light-reviews.com/fenix_ld10_r4/

A marvelous discovery for me.

The BIG difference between LD10 and LD20 is the battery life. In LD20 with 3000 mAh NiMh the runtime is 1:35-1:40 hours. In LD10 is 45 minutes. Both in Turbo mode. However, for me is a very good runtime. In the lower modes probably be a lot greater.

We live in a wonderful era of great flashlights.

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Which is almost the same with LD 20 R4 (194 Lumens). With nake-eye,
we probably cannot tell the different between these flashlights.
Fenix made a BIG improve on LD-10 R4 this time.
Cheer !!!.