# Zebralight H51Fc AA Floody Headlamp 85 CRI Is A Mighty Fine Light



## eh4 (Dec 15, 2011)

I ordered the thing a couple days ago, got it today. Paid the extra 25$ to expedite shipping of three lights. 
If you aren't looking for the brightest light, but rather extremely good quality, diffuse light then this little thing is a just, about, perfect. 
The lowest setting is about as bright as I'd want it with dark adjusted eyes, the small size makes it very easy to cover with two fingers and let just the right amount of light out... rated for 16 days of light at that level, amazing. Being lost in a mine will never be the same.
The next level up (the higher Low) is going to be fine for most tasks, I see doing a lot of cooking and camp chores at that level, rated for 3 days on a fresh AA. 
The upper and lower middle levels seem about perfect for reading and detail work to me, 10 hours and 26 hours, fantastic.
Finally for the real kicker I put the light on high and went out walking where it's a bit hazardous to walk, this 4000K 85CRI light makes dog manure stand out more plainly than daylight, it really does.
There's hardly a shade of brown that I care more about being able to spot outside, picking my way was no trouble at all.
Useful throw seems to be about 30 feet or so but of course that's not what this light is for.
Simply a fantastic light.


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## davidt1 (Dec 15, 2011)

Thanks for your impressions of the H51Fc. I bought my first high CRI light, a Quark Mini AA, a few weeks ago. While it's not a ZL light, I am actually using it as a headlamp. I like the tint very much and understand your liking of the high CRI tint.

I also find that for up-close tasks all I need is the medium mode which can run for hours no matter what light I use. Being able to get this kind of run time from a light you can actually carry in your pocket (after lanyard headband mod) is wonderful, isn't it? This reason alone is why I will never trade a ZL light for any bulky jockstrap headlamp.


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## eh4 (Dec 15, 2011)

You bet davidt1, your's and other's mods pics/articles have kept me on track to getting this light over the last month and a half. 
Really it's thanks to you and the other ZL fanatics that I paid so much attention to the possibilities of this light and that I understood exactly what I was getting ahead of time.
Read the stats and notice that while the hi CRI 4000k ZLs have the lowest lumens at highest settings, according the stats they end up producing more lumens than comparable ZL lights after you get down around the 26 hour setting.

The warmer tint, high CRI is just a game changer for me, so is the floody beam for that matter.
I have thought a lot about the efficiency of blue/green leaning lights (cool white) and read up about human eye responsiveness, and how nature tends to reflect warmer tones as well... Fact is that I see so much better with a warm light that it makes me wonder if just as there are varieties of color blindness in the population that there might be people with surpluses of certain cones. 
It's not just what you can report seeing consciously, but also how well your subconscious visual system responds, balance, peripheral vision, reflexes/emotional response, etc. I'll get out the slack line and do a little bit of 4000k balancing later for fun.
Sheer speculation but I think that these longer wavelengths are providing very good light whether they get counted as lumens or not on paper.


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## Bolster (Dec 15, 2011)

After my first experience with HCRI (two 4/7's lights) I'm beginning to wonder if I want to buy anything else but HCRI from here on out. I really want the H502w, but I wonder if there might be an H502c in the future.


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## BarryH (Dec 15, 2011)

You guys might want to check out the new headband that Klarus makes. It is excellent for the H501, H51, and other lights. I was at the going gear store (they are local for me) and picked one up. It has an elastic loop to hold the light so is very easy to insert or remove the light for hand held use. Also very comfortable with little nicer quality, thicker, and stretchier elastic. :thumbsup:


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## B0wz3r (Dec 15, 2011)

Bolster said:


> After my first experience with HCRI (two 4/7's lights) I'm beginning to wonder if I want to buy anything else but HCRI from here on out. I really want the H502w, but I wonder if there might be an H502c in the future.



I got one of the high CRI Preon 1's and two of the 123's, and am very happy with the tint.

I've been wanting one of the high CRI H51Fc's as well, but honestly can't justify it.

I too entertained similar thoughts of the high CRI warm tint, but have realized the neutral tinted lights I have still have their use and place.

Right now I'm away from my family working in a new job, with new snow and more to come. For this situation, the high CRI 4Sevens lights are excellent. I also did a comparison between them and my SC60w, SC50w+, and H51w and I still like them just fine. For one, they're brighter of course, but next to the high CRI Quark they have a pure white tint, and I'm sure there will be times where I'll prefer that to the warmer tint of the high CRI lights. As much as I like the new high CRI 4Sevens lights, my SC60w and SC50w+ are still my favorite EDC lights.


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## MrLi (Dec 15, 2011)

I ordered it last week but it was already on backorder for a couple of weeks 

Eagerly waiting to get my hands on one of the H51fc...thanks for writing down your experience with it.


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## eh4 (Dec 16, 2011)

yeah sorry, I think I snagged the last two available.
they are gifts and I actually ordered three, one of them is on backorder for me as well.


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## GaAslamp (Dec 16, 2011)

davidt1 said:


> Thanks for your impressions of the H51Fc. I bought my first high CRI light, a Quark Mini AA, a few weeks ago. While it's not a ZL light, I am actually using it as a headlamp. I like the tint very much and understand your liking of the high CRI tint.



It should be noted that these two flashlights have rather different tints, as they are of different color temperatures. The H51Fc has almost exactly the same color temperature as and a very similar overall tint to the H51Fw, while the high-CRI Quark Mini AA should be significantly warmer than either of the others mentioned (please let me know if you're observing something different in this regard). The H51Fc will render colors somewhat differently from the H51Fw, as it has more output, relatively speaking, in the non-blue portions of the spectrum, particularly in the red and orange range, but overall the difference is subtle unless you're real picky about those things. By the way, ZebraLight is very picky about the tint bins of the neutral Cree emitters they use in their "w" flashlights, which is probably why their color rendering comes close to that of the high-CRI Rebel used in their "c" flashlights.



eh4 said:


> Read the stats and notice that while the hi CRI 4000k ZLs have the lowest lumens at highest settings, according the stats they end up producing more lumens than comparable ZL lights after you get down around the 26 hour setting.



That's right, the Luxeon Rebel is less efficient than the Cree XP-G at higher output levels, but is actually more efficient at lower output levels. That was certainly a consideration when I decided to get my H51c, as I would be using the lower output levels most of the time by far anyway.



eh4 said:


> I have thought a lot about the efficiency of blue/green leaning lights (cool white) and read up about human eye responsiveness, and how nature tends to reflect warmer tones as well... Fact is that I see so much better with a warm light that it makes me wonder if just as there are varieties of color blindness in the population that there might be people with surpluses of certain cones.



Maybe there's something to this, but unpinning any differences between individuals would be the fact that typical cool white LEDs are lacking in certain areas of the spectrum (they're more efficient because they simply let more of the blue light from the die right on through). Cool white light that renders warm colors better than this certainly exists (e.g. natural incandescent sources such as the sun), and even some such LEDs have been made, although the latter are extremely rarely used in flashlights (e.g. McGizmo SunDrop) and are less efficient than the usual type of cool white LED.



BarryH said:


> You guys might want to check out the new headband that Klarus makes. It is excellent for the H501, H51, and other lights. I was at the going gear store (they are local for me) and picked one up. It has an elastic loop to hold the light so is very easy to insert or remove the light for hand held use. Also very comfortable with little nicer quality, thicker, and stretchier elastic. :thumbsup:



The only real complaint I have about ZebraLight is that their headbands are subpar, which is kind of sad for a company that semi-specializes in headlamps (and makes such great headlamps and flashlights). It's not a real big issue, though, because their headlamps work great with many other headbands, even miniaturized, improvised ones as davidt1 has shown us. The one from Klarus looks quite practical, as long as it's stable enough (i.e. more stable than the ZebraLight headband), but among commercial products I'd also suggest checking out the Nite-Ize headband, which is tough, versatile (can be used with AA or AAA class flashlights), stable even when running (for short distances--haven't tested it over long distances), and has worked very well for me. The band itself is not elastic, but I haven't found this to be an issue in the slightest (perhaps my skull is elastic? ).


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## eh4 (Dec 16, 2011)

I've just put the headband away and am working out the ergonomics of just the light and clip.

The clip is plenty stout to me, I was concerned that it would pop off of the body too easily, but it's pretty secure. 
If I catch the light on something real good then I imagine the clip will come off the body before it bends but the light weighs little enough that short of a high speed impact it's own inertia shouldn't ever work the clip off.


I've clipped the light underneath my baseball cap bill and that works great, offset to the right, will eventually get a second identical light and clip it underneath the bill on the left and see how the stereo floody set up works. Should be great for run times and more ambient effect for detail work. 
The only potential problem I see here is that I wouldn't wear it this way if I was in a situation where I was likely to be bumping my head, as the aluminum body sits right at my temple, but the lighting is great, no glare.

Clipped to the neck of my tee shirt I can pull the light up just enough that the shirt bunches a little bit where the clip is tight, right at the balance point of the light, and it'll sit sideways very stably and light up everything in my neutral working position.


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## GaAslamp (Dec 16, 2011)

eh4 said:


> I have thought a lot about the efficiency of blue/green leaning lights (cool white) and read up about human eye responsiveness, and how nature tends to reflect warmer tones as well... Fact is that I see so much better with a warm light that it makes me wonder if just as there are varieties of color blindness in the population that there might be people with surpluses of certain cones.



By the way, under low levels of lighting there are also the rods to consider, and if you read up about those, you'll see that LEDs typically have poor output at the relevant frequencies, particularly near the peak where it counts the most. While the same applies even to high-CRI LEDs, they are usually significantly improved over normal-CRI LEDs in this respect, which is one reason their CRIs are higher; I'm not sure whether this is true for the high-CRI XP-G specifically, but it is for the high-CRI Rebel that ZebraLight uses. Theoretically, this should improve the perceived brightness at very low levels, and perhaps even somewhat at slightly low levels (i.e. mesopic vision).


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## B0wz3r (Dec 16, 2011)

eh4 said:


> I have thought a lot about the efficiency of blue/green leaning lights (cool white) and read up about human eye responsiveness, and how nature tends to reflect warmer tones as well... Fact is that I see so much better with a warm light that it makes me wonder if just as there are varieties of color blindness in the population that there might be people with surpluses of certain cones.
> It's not just what you can report seeing consciously, but also how well your subconscious visual system responds, balance, peripheral vision, reflexes/emotional response, etc. I'll get out the slack line and do a little bit of 4000k balancing later for fun.
> Sheer speculation but I think that these longer wavelengths are providing very good light whether they get counted as lumens or not on paper.



About 60% of all cones in the retina are the long wavelength (red), cones; about 25% are the medium wavelength (green) cones; about 15% are the short wavelength (blue) cones.

So in short, yes, we see warmer colors better as a result.

And there is individual variation in these proportions from person to person, so some people can have better red acuity or green acuity because of it. A late best friend of mine for many years who was an artist always said he could see multiple shades of red in what looked to me to be an otherwise uniform surface, such as the paint on a car.

Also, much of the information we process, not only visually but through the other sensory modalities as well, never makes it to our conscious awareness, but does have affective influences. As a quick example, in one study on subliminal perception, people watched a fake TV ad for a product. One half saw a subliminally presented image of an adorable little girl playing with a puppy, while the other half saw a subliminally presented image of a tarantula eating a mouse. Both groups completed a rating survey of the product afterward. The girl/puppy group rated the product significantly more favorably than did the tarantula/mouse group, whose average overall rating was negative instead of positive. 

While that is a more complex example, it does also have correlates in disorders such as Seasonal Affective Disorder, which has been linked to diminished activation of the suprachiasmatic nucleus and other structures in the limbic system such as the amygdala, via the retinohypothalamic pathway from lack of full spectrum light stimulation. So even on a basic perceptual level, at the level of the hypothalamus and limbic system, the wavelength consistency of the light we're exposed to does have cognitive and emotional effects.


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## Harry999 (Dec 16, 2011)

Interesting thread. Oh just to add for those interested in a secure headband I have found the one that works for me is the Nite Ize one. Whether it is a H51c, a H501w or a Fenix MC11 (modded with a warm Lee Filter) that headband has met and exceeded my expectations.


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## GaAslamp (Dec 16, 2011)

eh4 said:


> The clip is plenty stout to me, I was concerned that it would pop off of the body too easily, but it's pretty secure.
> If I catch the light on something real good then I imagine the clip will come off the body before it bends but the light weighs little enough that short of a high speed impact it's own inertia shouldn't ever work the clip off.



I've been EDCing my very similar H51c in my pants pocket, clipped to the edge, for several months now, and thus far have experienced nothing to indicate that the clip will work loose on its own when subjected to the constant motion of walking as well as getting bumped with some force now and then. On the whole, it seems like a pretty tough, useful clip to me.


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## Bolster (Dec 16, 2011)

B0wz3r said:


> About 60% of all cones in the retina are the long wavelength (red), cones; about 25% are the medium wavelength (green) cones; about 15% are the short wavelength (blue) cones...



This is why I come here. Free education!! Very interesting stuff.

So there may actually be valid reasons why I'm happier and more content working with a warmer light in crawlspaces, whereas blue-tints have made me feel nervous and fretful, and just want to get the heck out. It's only a correlation, but there might be a reason for it?


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## robostudent5000 (Dec 17, 2011)

B0wz3r said:


> About 60% of all cones in the retina are the long wavelength (red), cones; about 25% are the medium wavelength (green) cones; about 15% are the short wavelength (blue) cones.
> 
> So in short, yes, we see warmer colors better as a result.
> 
> And there is individual variation in these proportions from person to person, so some people can have better red acuity or green acuity because of it. A late best friend of mine for many years who was an artist always said he could see multiple shades of red in what looked to me to be an otherwise uniform surface, such as the paint on a car.



i guess that's why red cars get more speeding tickets and stop signs are red.


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## Bolster (Dec 17, 2011)

robostudent5000 said:


> i guess that's why red cars get more speeding tickets and stop signs are red.



LOL, clever! Now if you would please explain the "red light district."


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## B0wz3r (Dec 17, 2011)

Bolster said:


> This is why I come here. Free education!! Very interesting stuff.
> 
> So there may actually be valid reasons why I'm happier and more content working with a warmer light in crawlspaces, whereas blue-tints have made me feel nervous and fretful, and just want to get the heck out. It's only a correlation, but there might be a reason for it?



Yes actually. The retinohypothalamic pathway I mention above is the primary pathway for the environmental signal to our internal biological clock. There are a specialized group of retinal ganglion cells that don't connect to any of the photoreceptors and are themselves sensitive to light, but only to longer term changes in light levels. It's their signals to the brain that synchs our biological clock to the day-night cycle, and they are most sensitive to shorter wavelengths, in the blue range. So blue light stimulates them, sending a signal to the brain telling us it's daytime, but they are insensitive to longer (warmer) wavelengths such as yellow and red, and so are not activated by it. As a result, the don't stimulate mechanisms in the hypothalamus that increase things like basal metabolism rate through krebs cycle activity, production of hormones such as melatonin and per and tim that are integral in regulating our circadian rhythm, so we don't get physiologically activated by warm tints the way we do by cool tints.

I'd also suspect that there's other cognitive and emotional issues at work to there B, but I'm no clinician, so I'll leave that between you and your therapist! 



robostudent5000 said:


> i guess that's why red cars get more speeding tickets and stop signs are red.



This actually isn't about perception; rather, it's about how we categorize and structure information in memory, and access that information as a result. There is a very weak link associated in that people tend to prefer warmer colors such as red, but that's about as far as it goes. Rather, red is what is known as a 'prototypical' color, a 'best example' when we're asked to think of a color. This is because red is also a commonly occurring color in the environment that has important implications for survival. Generally, in nature, red means "don't mess with me, I'm (insert one: dangerous/poisonous/lethal)... So our brains and social customs have evolved to pay more attention to red things than blue or green things, so we notice them more easily and pay attention to them more.

As an interesting little trick, when I cover knowledge structure and organization when I teach intro cognitive psych, I do a fun little demo in class... I tell students I can read their minds... and ask them to think of a tool, the first tool that comes to mind... then I also ask them to imagine that tool being some color, the first color that comes to mind... typically about 75% of the class end up thinking of a red hammer, because red is the 'best example' of a color, and a hammer is what most people think of when asked to think of any tool, because it's generally thought of as the 'best example' of the idea of 'a tool'. The rest usually think of a red screwdriver, or a green screwdriver, because those are the second-best examples of those same categories.


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## Gregozedobe (Dec 18, 2011)

Just to add to the "colour" education, I read a study somewhere that claimed in one-on-one competitions (boxing, wrestling etc) the competitor wearing red had a distinct (small but measurable) advantage over their opponent. IIRC They postulated that the colour red had some kind of effect on both the opponent AND The judges perception of the contest.

So if you want to intimidate someone with your super-sharp crenulated bezel, make sure your flashlight is anodized red :devil: (this para added just to retrieve the thread back to a flashlight related topic)


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## eh4 (Dec 20, 2011)

Wow some good information has come up here, thanks guys for the informative replies.
I agree about blue leaning lights making me more nervous in crawl spaces, and red leaning lights making me more comfortable in the same spaces.
As for the Red Light District, it's my understanding that red light has been used for those markets because red light makes everybody look similar, and healthy... Someone with skin tone preferences would just see shades of red, and an unhealthy looking person would look pretty good, and red.


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## qcent (Dec 27, 2011)

Hello all, I am very new to flashlights so forgive me if my questions seem uninformed. (most likely they are)

I recently received the H51Fc myself and even though I love the color tint. My run time on H1 seems to be lower than I expected. My light seems to step down to the lower modes faster than my SC51 on the same type of batteries. 

Does anyone else see the same thing? The contacts seem to get dirty a lot for some reason, even with cleaning. 

I am thinking perhaps its the batteries, I am using Lenmar 2500mAh. So I just ordered some Eneloops along with a smart charger capable of charging single cells.


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## eh4 (Dec 31, 2011)

I have nothing to really compare to my H51Fc, sorry.
What I have noticed is that H1 and H2 don't look That different. As has been mentioned before you need 4x the light to see twice as far, and for most people it's going to take about 3x the light to seem much brighter.
I can really tell the difference between H1 and H2 by moving to the edge of what I can distinguish on H2 and then bumping it up to H1.
The reason that I mention all of that is that I find that using H1 wipes the battery out pretty quick. H2 should be good for about 2.4 hours and M2 about ten times longer than that.
I still find L1 and M2 to be the most used settings for my uses... 72 hour and 24 hour ratings. I don't have the patience to see how accurate the ratings are ;-). I'm basically looking for excuses to run the batteries down, messing with H1 till there is no difference between H1 and H2, then running it till there's no difference between M1 and H2... The light will still run for longer than I can stand to leave it running on L1 at that point, and L1 (72 hour rating) is half of what I got the light for originally. (Great for finding night crawlers btw.)

Definitely get the Eneloops, flashlights aside they are about the smartest purchase I've made in quite a while. I can see why they are not found on store shelves much, they'll knock AA sales down to almost nothing.


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## qcent (Jan 4, 2012)

I received the smart charger along with some eneloops and I have to say that the H51Fc performs as it should now. I use both the H51Fc and the SC51 for biking home from work and they work great in combination. It's about a 45minute ride home, so I can go max all the way. 

Lesson learnt: Lights are only as good as it's power source.


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## iron potato (Jan 13, 2012)

Got my H51Fc, trying out the runtime mated with PowerGenix NiZn AA 2500mWh, on it at H1, around 30mins mark, still on full output, I measured using IR temperature probe, was 58.3°C on the heatsink area  36mins mark, getting lower output, around M1 I would guess, at 40mins temperature drops to 41°C output were around M2, 45mins mark output were around L1.

I think its just about it, the battery capacity is around 1500+mAH anyway. Took out the battery, measured 1.36v, depleted :huh:

I'll try on Eneloop again.

Edit : Fresh Eneloop runtime also around the same, around 30mins mark, temp @ 55.2°C, eventually output & temp dropped after 35mins mark.


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## eh4 (Jan 13, 2012)

I've determined that for myself H1 is only useful on the rare occasions that H2 isn't enough. H1 isn't that much more bright to warrant the short battery life and the heating up of the body. H2 will run cool for my light and H1 heats up quick. I'd much rather have the 2.4 hour 60 lumen than driving the light hard, heating it up (120 something lumens) and not even get that much more useful light.

Ultimately it's a work light for me that can be used as an area light, the 10 hour (M1), 26 hour (M2), and 72 hour (L1) settings continue to be the levels that I use with this light. 16 day (L2) gets some use in the middle of the night and 2.4 hour (H2) gets very brief use when looking into a dark corner with daylight adjusted eyes, but H1 is just an almost unnecessary handwarmer setting to me.


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## iron potato (Jan 14, 2012)

I concurred with H2 or M1 already enough for my work light, itch to test the runtime  I also don't wish to stress out the light & the battery too often 

Liking more & more to ZL UI... becoming ZL fanboy day by day :devil:


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