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SUREFIRE K2 KROMA
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SureFire K2 Kroma, retail $299.00 (www.surefire.com...)
Manufactured by SureFire (www.surefire.com)
Last updated 02-06-12

SureFire is well-known for making the toughest and brightest personal and tactical lights in the world, and the new K2 will not disappoint you.

The K2 has a white Luxeon III LED, eight 3mm blue LEDs, and eight 3mm red LEDs to make its light, feeds from two CR123A lithium camera batteries, has a pushbutton on the tail for momentary and twist-tailcap for constant-on, and most importantly, has a selector ring on the barrel to select any of the LED colors (red, white, blue, red+white, or blue+white). The LEDs and optic are protected by a slightly domed pyrex glass window (or "lens" if you are more comfortable with that term, even though it does not focus or defocus the light in any manner).

The white Luxeon III is behind a TIR (total internal reflection) optic to ensure that the primary beam is perfectly focused—no dark holes, hot spots, or shadows. Red and blue secondary LED beams also feature two output levels suitable for operations requiring minimal light; for preserving night vision while navigating, tracking, map reading, or other close work; or for negotiating outdoor terrain without disturbing wildlife (many animals cannot see red light).

SIZE

The K2 comes with batteries already installed, so you'll be ready to roll right away. If necessary, turn the tailcap clockwise (as if tightening it) to disengage the LOTC (Lock Out TailCap) function.

Partially depress the tailcap button to momentarily activate the colored LEDs — blue if the selector ring behind the head is turned counterclockwise (as the flashlight is pointed away from you) or red if this ring is turned clockwise (as the flashlight is pointed away from you), or low-intensity white if this ring is positioned to its center (as the flashlight is pointed away from you).

To obtain high intensity white, press this button more firmly.

You can also turn the tailcap clockwise to get low-intensity white in continuous or hands-free mode, and turn it clockwise some more to get high-intensity white in the same mode. When in high-intensity white mode, you can rotate the selector ring to add the blue or red LEDs to the white.

If you have low-intensity white running, you can turn the selector ring to obtain low-intensity red, high-intensity red, low-intensity blue, and high-intensity blue.

The K2 features a LOTC to prevent the flashlight from turning itself on when packed in a box, bag, camping kit, etc. Unscrew the tailcap three turns from the fully tightened position to engage the LOTC (on the sample I'm testing, 2 1/2 turns from fully tightened does the trick), and tighten it back up when you're ready to use your K2 again.

The K2 can be held overhand (like a police officer usually holds his or her flashlight), or underhand (like how most other people hold a flashlight). When held in an overhand grip, your fingers curl around the barrel, and your thumb automatically falls over the tailcap switch.

You can also use the K2 with a pistol, as the LEDs inside won't blow up when the gun recoils (kicks) every time it is fired. I'm no firearms expert though.

To change the batteries in your K2, unscrew the bezel, throw it in the {vulgar term for toilet}, and flush it away...O WAIT, THAT'S THE GOOD PART!!! So just set it aside instead.

Tip the two dead CR123A cells out of the barrel, and dispose of or recycle them as you see fit. Lithium batteries do not like water, so please do not dispose of them in a trout-filled stream or by flushing.

Insert two new CR123A cells in the barrel, flat-end (-) negative going in first — facing the tailcap of the flashlight.

Screw the bezel back on, finger-firm tightness only.
Aren't you glad you didn't flush away that bezel now?

You can also tail-feed this flashlight; just unscrew & remove the tailcap, drop the dead batteries out, insert two new ones with the button-end (+) positive going in first, then screw the tailcap back on — and unscrew it slightly when your K2 springs to life.

Current measurements are as follows:

819mA (white, high)
1,023mA (white & red, high)
1,006mA (white & blue, high)

All measurements were taken on my DMM's 4A scale.
I was not able to measure the other modes because the circuitry necessary for those modes resides in the tailcap, and I have to remove the tailcap to measure current.

Battery disacharge analysis

Here is a battery discharge analysis of the white LED on high mode.
As you can see, it operates for ~2 hours 15 minutes (to 10% intensity).
The battery brand used for this test is "Powerizer". I used this brand of CR123A cell because I do not have any other brands.

Approximately one hour into the test, the bezel temperature was measured at 109°F (42.8°C).
I used a noncontact IR thermometer for this measurement, so I had zero chance of bumping something and queering the test.
Ambient temperature in the testing area at this time was 80°F (26.7°C).

Picture of the business-end of the K2, showing the LEDs, the TIR optic, and the lightly scalloped bezel.

The K2 is extremely well-made and engineered. The same SureFire quality you've come to expect from their personal and tactical lights is built into this product. The exterior finish is a black type 3 hard anodize ("HA-III" as us flashlight nuts know it), and there's a gold colored material (Chemcoat) inside the barrel to protect it against corrosion from water or bad battery juice.

One of the things I noticed quickly is that the K2 has a lightly "scalloped" bezel, so if the light is set face-down while it's burning (well, LEDs don't "burn", they just emit light, but you get the idea), some light still escapes and you can easily tell it's still turned on, even if you set it down on a completely flat surface like a tabletop or countertop. No more ruined and wasted batteries from your setting the light down and not realising it's still on.
(Yes, I really did that — to a SureFire KL2 if I remember right!)

When the tailcap was removed, the flashlight was relieved of its batteries, and that dreadful suction test was performed, the flashlight held a vaccume (vacum, vaccuume, vaccumn, vaccuummnne, vacuum, etc.), so I believe it is both weather- and water-resistant. I also took the bezel (head) off and performed the same test, with the same results. Even when the button was clicked, there was no air leakage. So you need not be concerned at all about using the K2 in rain or snow, and water landings will not kill it either.

I smacked the K2 against the concrete floor of a patio ten times (five against the side of the bezel, and five on the side of the tailcap) and was not able to damage the flashlight in any manner, other than causing some rather minor gouging to the bare Metalgreymon — er — the bare Metalstingmon — um that's not it either...the bare Metalwormmon...er...uh...wait a sec here...THE BARE METAL (guess I've been watching too much Digimon again!

— now I'm just making {vulgar term for feces} up!!!) on the sides of the tailcap and bezel where it was struck. No optical, mechanical, or electrical malfunctions were detected.

I tried to cut through the K2 with the blade of a Gerber folding knife, and was not successful.
Would I really try to cut up a brand spanken new flashlight that costs almost $300.00?
You bet your sweet patootie I would, if it's in the name of science.

There is knurling (texturising) along the barrel and on the tailcap, and some ribbing on the mode setting ring itself; these help aid in retention (the ability to hold the flashlight when your hands are cold, oily or wet). You can use it with the Rogers/SureFire technique or the Harries technique. But remember, I don't own a gun or anything that even remotely resembles a gun, so I cannot show you with pictures what these grips look like.

The K2 has a stiff stainless steel clip with a plastic or nylon gripping piece on the end.

The beam this sample produces (in white LED mode) is a pure white in color, with none of that obnoxious purple, blue, yellow, or "rotten squid urine green" tint anywhere in it. Not in the hotspot, and not in the corona.

PWM (Pulse Width Modulation) (a method used for dimming LEDs) was *NOT* detected when the standard test for detecting the presence of it failed. The pulses could be much too fast for an optical detection method to detect them, or the K2 could use a resistive method for dimming its lamps.

The selector ring makes a rather noticeable "click" sound whenever it is turned. This does *NOT* make it a bad flashlight — don't get me wrong here — just one that might not be appropriate to use in extra-covert situations or in other situations where even a little noise would not be desired.

I like the two-level red - I can skulk around at night without waking my sister up if she's sleeping on the couch. I would however add a mode where the red & the blue LEDs can be operated simultaneously; not unlike the blood tracking mode of the Gerber Carnivore. This would allow one to have a better ability to track down wild animals they have hosed down at night but have not killed — allowing you to finish the job and not having an injured animal limping through the forest for perhaps a number of days. This would be more humane, as well as allowing you to "bag" your game more effectively.

Beam photograph (white) at ~12".
Measures 63,900mcd (low) and 1,730,000mcd (high).

Beam photograph (red + white) at ~18".
Measures 1,770,000mcd.

Beam photograph (blue + white) at ~18".
Measures 1,771,000mcd.

Beam photograph (blue) at ~12".
Measures 2,220mcd (low) and 11,290mcd (high).

Beam photograph (red) at ~12".
Measures 1,460mcd (low) and 9,670mcd (high).
All measurements were taken on a Meterman LM631 light meter.

Photograph showing the K2 Kroma being used with a gun in a "combat grip".
Note that this is a BB pistol, not a gun that shoots real bullets.
BB gun was used here for representative purposes only.

Spectrographic analysis of the LED in this flashlight (white).

Same as above (high mode); newer spectrometer software & settings used.

Same as above (low mode); newer spectrometer software & settings used.

Spectrographic analysis of the LEDs in this flashlight (blue).

Same as above; newer spectrometer software & settings used.

Spectrographic analysis of the LEDs in this flashlight (red).

Same as above; newer spectrometer software & settings used.

Spectrographic analysis of the LEDs in this flashlight (white + blue).

Same as above; newer spectrometer software & settings used.

Spectrographic analysis of the LEDs in this flashlight (white + red).

Same as above; newer spectrometer software & settings used.

Spectrographic analysis of the white LED (low); yet newer spectrometer software & settings used.

Spectrographic analysis of the white LED (high); yet newer spectrometer software & settings used.

Spectrographic analysis of the red LEDs; yet newer spectrometer software & settings used.

Spectrographic analysis of the blue LEDs; yet newer spectrometer software & settings used.

Spectrographic analysis of the white LED (low); spectrometer's response narrowed to a band between 430nm and 480nm to pinpoint native emission peak, which is 455.330nm.

Spectrographic analysis of the white LED (high); spectrometer's response narrowed to a band between 430nm and 480nm to pinpoint native emission peak, which is 448.683nm.

Spectrographic analysis of the red LEDs; spectrometer's response narrowed to a band between 620nm and 670nm to pinpoint peak wavelength, which is 644.210nm.

Spectrographic analysis of the blue LEDs; spectrometer's response narrowed to a band between 440nm and 490nm to pinpoint peak wavelength which is 462.555nm.

USB2000 Spectrometer graciously donated by P.L.

ProMetric analysis

Beam cross-sectional analysis (white LED).
Image made using the ProMetric System by Radiant Imaging.

Beam photograph at ~10 feet.

Those rectangular graphic things are marquees from:
Midway ''Omega Race''
Sega ''Star Trek''
Williams ''Joust''
Venture Line ''Looping''
Universal ''Mr. Do!'s Castle''
Jaleco ''Exerion''
Gremlin/Sega ''Astro Blaster''
Atari ''Tempest''
Gottlieb ''Q*bert''

upright coin-op arcade video games from the 1980s.

TEST NOTES:
Sample was sent by PK of SureFire (it was accidentally sent to my old Seattle address, and after it was returned to SureFire, it was sent here), and was received on the afternoon of 10-05-06.

Product was made in the United States. A product's country of origin really does matter to some people, which is why I published it on this web page.

UPDATE: 10-13-06
I used the K2 on low-intensity red LED mode at ~6:15am PDT today to get from my room to the outdoor patio in place of the LRI Proton that I use every day in red LED mode, and it functioned beautifully.

UPDATE: 10-19-06
It has been reported by a user of the K2 that it is ok to use Li:ION rechargeable R123A or RCR123A cells in the K2, even though the total system voltage is +8.4 volts, instead of +6.0 volts like you would find with primary lithium CR123A cells.

UPDATE: 10-28-06
One-handed operation in continuous-on mode is possible — though quite difficult. The tailcap has a fairly still action to it; you can still push the tailcap button quite easily though, so one-hand use in momentary mode is not a chore at all.

PROS:
Tough and durable construction like all SureFire products
Multiple lighting modes
Pyrex end-window ("lens") to resist scratches, not acrylic or other plastic
Waterproof — even submersible to 33 feet

CONS:
None that I have thus found

MANUFACTURER: SureFire
PRODUCT TYPE: Adjustable brightness/color tactical handheld flashlight
LAMP TYPE: Luxeon III LED, 3mm LEDs
No. OF LAMPS: 17 (1 Luxeon, 8 3mm blue, 8 3mm red)
BEAM TYPE: Varies with LEDs used
SWITCH TYPE: Push tailcap momentary, twist tailcap continuous
BEZEL: Lightly scalloped; pyrex glass window protects LEDs and optic
BATTERY: 2 ea. CR123A cells
CURRENT CONSUMPTION: 1,023mA max (unable to measure lower modes)
WATER- AND PEE-RESISTANT: Yes
SUBMERSIBLE: Yes, to at least 33'
ACCESSORIES: 2 CR123A cells
SIZE: 5.50" long, ~1.50" diameter at its widest point
WEIGHT: 4.90 oz.
WARRANTY: Lifetime, except batteries

PRODUCT RATING:

SureFire K2 Kroma * www.surefire.com...

Do you manufacture or sell an LED flashlight, task light, utility light, or module of some kind? Want to see it tested by a real person, under real working conditions? Do you then want to see how your light did? If you have a sample available for this type of real-world, real-time testing, please contact me at ledmuseum@gmail.com or send your potential victim to:

Craig Johnson
c/o The LED (and Laser) Museum
490 Forastera Circle
Sacramento CA. 95834-2709
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