Emisar D1 / D1S review

Emisar D1 / D1S

Hank of Intl-Outdoor sent me a D1 and D1S to play with, and people have been asking for a review…

Both lights are single-emitter compact throwers. The D1 is smaller with less throw, while the D1S is larger with more throw. Both lights out-throw almost everything else in their size class.

Disclaimer: I’m not an impartial reviewer. I made part of the firmware for these lights and may be doing more development for Emisar in the future.

Note 2: The lights aren’t wobbly or uneven… my photo box just isn’t very flat on the bottom.

Official Specs


  • CNC machined from aircraft-grade aluminium
  • Smooth aluminum reflector
  • Anti-reflective coated glass lens
  • Unihead construction
  • High lumen output and low moon output
  • Ramping interface
  • Electronic soft touch switch (ALPS)
  • Beryllium-Copper springs with 45% IACS superior to stainless steel alloys used for springs with only 2% IACS.
  • Temperature step-down
  • Waterproof and dustproof to IP67 standard (up to 1 meter)
  • Default 18650 body with optional 18500 or 18350 battery tube
  • Dimensions: 105mm(length) * 35mm(head) * 24mm(body)
  • OTF lumen output at start-up
    • XP-L HI : 1300lm / Lux : 43000cd
  • Price: $40

D1S: None have been published yet. (ETA: soon)


Note: My lux meter seems to measure throw a bit lower than the numbers other people get.

D1 Output:

  • Beam type: Spot plus spill, wide corona with four dim flower petals
  • Power: Probably around 6 Amps (not measured)
  • LEDs: Cree XP-L HI 3A ~5200K
    • ~30 cd / lm
    • Lux: 40 kcd / 400 m
    • Min: 0.6 lm
    • Max: (measured at start, not at 30s)
      • 1305 lm (30Q 18650 @ 4.17V)

D1S Output:

  • Beam type: Spot plus spill, small bright corona
  • Power: Probably around 6 Amps (not measured)
  • LEDs: Cree XP-L HI 3A ~5200K
    • ~93 cd / lm
    • Lux: 124 kcd / 703 m
    • Min: 0.6 lm
    • Max: (measured at start, not at 30s)
      • 1334 lm (30Q 18650 @ 4.17V)

D1 Dimensions:

  • 18650 length: 104.2 mm
  • Bezel diameter: 34.9 mm
  • Head diameter: 37.2 mm (widest point)
  • Body diameter: 23.9 mm
  • Clip groove diameter: 22.5 mm
  • Clip groove width: 3.0 mm
  • MCPCB shelf: ?? mm thick
  • Driver: 22.3 mm diameter, 1.6 mm thick PCB, ~19.3 mm x ~2.5 mm space for components.
  • Maximum cell length: 67 mm
    (protected cells may not fit)

D1S Dimensions:

  • 18650 length: 127.5 mm
  • Bezel diameter: 50.0 mm
  • Pill diameter: 36.0 mm
  • Body diameter: 23.9 mm
  • Clip groove diameter: 22.5 mm
  • Clip groove width: 3.0 mm
  • MCPCB shelf: ?? mm thick
  • Driver: 22.3 mm diameter, 1.6 mm thick PCB, ~19.3 mm x ~2.5 mm space for components.
  • Maximum cell length: 67 mm
    (protected cells may not fit)

Host / Build:

  • Weight: ?? g
  • Switch type: Momentary / electronic side switch
  • Body material: Hard anodized aluminum: black, grey, or green
  • Lens: Glass, AR coating TBD
  • Anti-roll (slightly) and tail-standing capable (but D1S is a bit top-heavy)
  • Waterproof to IPX-something (?) (not yet tested)
  • Premium BeCu (Beryllium Copper) springs capable of high current without sagging
  • Reflectors:
    • D1: TBD x TBD mm
    • D1S: TBD x TBD mm


  • Operating voltage: 2.8V to 4.35V
  • D1 battery: One 18650, 18500, 14500, 18350, or 16340 cell (with matching tube)
  • D1S battery: One 18650 cell (tube on mine is slightly different than D4/D1)
  • Parasitic drain: ~0.02 mA (17 years to drain a 3000mAh cell)
  • Low-voltage protection: Yes
  • Thermal regulation: Yes
  • Power can be locked out by loosening the tailcap, or by entering a lock-out code on the button
  • Reverse polarity protection is on the driver, but it might not protect the cell. Don’t put the battery in backward, or it may permanently kill the battery.


The interface is the same as the D4 V2, a simplified version of Narsil’s ramping UI:

From off:

  • 1 click: Turn on at the last-used mode.
  • 2 fast clicks: Turn on in the highest mode.
  • Press and hold: Ramp up from the lowest mode.
  • Loosen and tighten the tailcap, then click: Turn on at the highest regulated mode (~130 lm).

While on:

  • Press and hold: Ramp up or down in last-used direction. Release and quickly hold again to change direction.
  • 1 click: Turn off.
  • 2 fast clicks: Shortcut to or from highest level.

Other actions:

  • Loosen tailcap: Turn off completely, and lock out power.
  • 3 fast clicks: Battcheck mode. Blinks out volts, pauses, then blinks out tenths of a volt. So, 4.2V would blink 4 times, pause, then blink 2 times.
  • 4 fast clicks: Momentary mode. Light will run at highest level when the button is pressed, and will stay off otherwise. Enter 4 fast clicks again to exit.
  • 6 fast clicks: Soft lockout. Light won’t respond again until you do another set of 6 fast clicks.
  • 8 fast clicks: Beacon mode. Lights up at 30% for half a second, pauses for 2 seconds, then repeats. Click to exit.
  • 10+ fast clicks then press and hold: Thermal config mode. Hold the button until it gets to the action you want:
    • Blinks out current temperature limit. Release button to exit with no changes, or keep holding to continue.
    • “Buzzes” for 2 seconds. Release button to set temperature limit to maximum, or keep holding to continue.
    • Light goes to turbo. Hold button until the light feels hot enough, then let go to set a new temperature limit.

From battcheck mode:

  • 1 click: Off.
  • 2 fast clicks: Thermal readout. Shows current driver temperature (in C or something close to C, I think).

From thermal readout mode:

  • 1 click: Off.
  • 2 fast clicks: Turbo.

This driver also has low-voltage protection. At 3.0V it’ll drop to the lowest level, and at 2.8V it’ll shut itself off as far as possible. It still has a very small amount of parasitic drain though, so don’t leave it in post-LVP mode for months or years at a time. It would be a good idea to change the battery within a few days, or unscrew the tube to cut power.

Here is the UI in diagram form:


The Emisar D1/D1s comes in the same type of box as the D4, except slightly bigger to fit the larger lights. It’s a simple but nicely padded cardboard box with foam cutouts to hold the light and O-rings. The box could potentially get dented during shipping, but the light inside should be pretty safe.


The D1 shorty tube is sold separately. I don’t know if the D1S will have any shorty tubes, or if the production model will be compatible with the D4/D1 tubes.

Comparison to other lights

These lights are somewhat unique, since they both out-throw almost everything in their size class.

  • The D1 is almost up to the performance of a BLF X6v2, except it’s as small as the BLF X5. I’ll probably be leaving the X5 and X6 at home now and using a D1 instead.
  • The D1S has been compared to a C8, but that’s not quite right — it’s significantly throwier than a C8. It’s more like a modded old HD2010 if anyone remembers that. In terms of lux, the throw is slightly higher than the top-of-the-line “throw king” from a few years ago, the Olight SR90 Intimidator. Except the D1S is a fraction of the size and a fraction of the price and has a nicer interface.

Here are a few pictures of the D1 and D1S next to some other lights, for size reference:

Emisar D4, D1, D1S, and D4 shorty.

Emisar D1 shorty, D4, and D1S.

BLF X5, Emisar D1, BLF X6v2. Shown in order of least to most throw.

Reflectors for BLF X5, Emisar D1, BLF X6v2. Shown in order of least to most throw.

BLF X6v2, C8, Emisar D1S. Shown in order of least to most throw.

Reflectors for BLF X6v2, C8, Emisar D1S. Shown in order of least to most throw.

[Jax Z1 vs D1S pic]

Host, Components, and Build Quality

The D1S uses a different battery tube than the D4 and D1. It’s very similar, but the threads on the front end start a bit sooner and go a bit longer so they are not interchangable.

The D1S would look cute with a shorty tube, but it doesn’t make electrical contact. The D1 works with the D1S tube, but it doesn’t screw in far enough to be waterproof.

The body tube has square threads which come fully lubed. Same as the D4, except that the D1S tube has an extra thread or two on the front end, which makes it incompatible with D4/D1 heads.

The D1 shorty tube is pretty much the same, except shorter. Nothing changed, so here’s a recycled pic of it from my D4 review:

Like the D4, the tail PCB is either press-fit or glued. There is no retaining ring. This makes the light smaller but harder to modify. I doubt the tailcap will need mods though.

The buttons stick out a little, just like the D4. It can be activated accidentally, but there are two ways to lock the light to prevent issues when carried in a bag or a pocket. Use the lock-out features! Unlike the D4, accidental fires are unlikely because the D1/D1S generate less heat, have more thermal mass, and spread their light across a wider area at the bezel.

The lens is AR-coated, but it’s some type of coating I’m not familiar with. It doesn’t make the beam turn green, and it doesn’t produce a blue halo. Oblique reflections off the lens appear amber-tinted instead of blue-tinted, and the beam still looks nice.


The new Emisar anodizing texture deserves some special attention. Instead of anodized metal, it feels a lot more like stone, or like very hard velvet. It also picks up scuffs a lot easier, but they seem to rub off without much effort. It’s very grippy.

Old / smooth texture

New / rough texture



I find the D4 to be the nicest-looking light of the Emisar line so far, with well-balanced proportions in 18650 form. With the 18350 tube it’s a bit stubby, but in a cute kind of way. I’d even call it adorable if it wasn’t so blindingly bright.


The D1’s appearance is mostly similar to the D4, but with a bigger head. Its proportions are still pretty balanced though, it comes in some nice colors, and it really feels well-designed. Compared to the D4 it seems less cute and more serious, but is regardless still a handsome light.


TBH, the D1S is a bit odd-looking.

I can’t quite put my finger on why exactly, but something about its strictly utilitarian minimalist design makes it seem distinctly different than other lights. It’s like it sheds a pretense of being aesthetic in nature and instead is unabashedly functional in an unromantic and frugal kind of way. It has not a single detail which can truly be called fanciful or cosmetic, posh or indulgent. Even the label on its tailcap serves a practical purpose, to indicate make, model, and what it does. Not unlike the first few days of owning a label maker, in which everything in the house receives plain labels like “table”, “door”, or “cat” (sorry about that, Mister Bigglesworth). Its strict adherence to purely pragmatic plain-ness is kind of an aesthetic of its own, like manufactured buildings made entirely of right angles and concrete. Or, more appropriately, like a rocket which consists only of an exhaust cone and a column of fuel.

I kind of like it better in 18350 shorty form, because then it’s even more blatant that it’s mostly just a big reflector with a power source and a shell, and really challenges traditional ideas of what a flashlight is supposed to look like.

It is, regardless, very good at what it does… but “what it does” is not “look pretty on a shelf”. It’s made to be used.


The D4, D1, and D1S all use fast 3-level PWM at 15.6 kHz to adjust brightness. Low levels oscillate between 0 mA and ~350mA, while higher levels oscillate between ~350mA and full power. The PWM is far too fast to see during use, but a child with good hearing might be able to hear a faint high-pitched tone.

Actual speed may vary from about 15.3 kHz to 15.7 kHz.

Thermal Regulation

Both lights have full thermal regulation. However, it may not activate for over a minute on the D1 because it takes a while to get hot… and it might not activate on the D1S at all, because the host is almost perfectly tuned to handle the heat on turbo without getting too hot.

However, the temperature limit is user-configurable, so you can tune it to fit your preferences.

First, a graph of the D4’s thermal regulation for reference. It stepped down very quickly due to its high power and very limited thermal mass:

Then for contrast, the D1 by itself… it steps down much more slowly and gradually:

Let’s add the D1S too. It didn’t really need to be regulated at all, which shows the effect of having more thermal mass and surface area:


To give an idea of the beam shape, I took pictures at five levels of exposure. My camera isn’t very fancy though, so they’re the automatic settings at –2, –1, 0, +1, and +2 stops, in that order.

Emisar D1:

Emisar D1S:


Output varies from about 0.6 lm to about 1300-1350 lm, with 150 ramp steps between. The ramp is visually linear, so the steps follow a curve approximately matching a graph of “x^3”. The upper levels ascend slower than on the D4, because the highest mode is about 1300 lm instead of 4000 lm. However, the ramp itself was calculated for a ceiling of 1500 lm, so the D1 and D1S should appear very close to linear while the D4 has more of an “elbow” in the middle of its ramp.

The ramp takes about 2.5s from one end to the other. It goes at a rate of one ramp step per timer tick, and the timer ticks happen every 16ms. This is a pretty comfortable speed during use, fast enough to quickly reach any desired level, but slow enough for reasonably precise control.


Runtimes will be approximate because the ramp is too smooth to be able to stop reliably at any particular level.

With a 3000mAh cell:

  • Standby: 0.02 mA / 17 years
  • Lowest mode: ~0.6 lm / 7.0 mA / 18 days
  • Medium mode (lvl 65): ~130 lm / 350mA / 8.5 hours
  • Highest mode: ~1300 lm / about 6 A / about 30 minutes

The output on the low levels (from moon to ~130 lm) should be fairly stable as the battery drains. The output on turbo will drop quite a bit over time due to heat, voltage sag, and thermal regulation.

On the medium and high modes, from ~130 lm to maximum, output will drop over time proportionate to how bright it is. The brighter it is, the steeper the slope as output declines with battery voltage. Performance in these modes is a hybrid between current-controlled and direct-drive, so the typical direct-drive sag becomes more prominent as the light goes into higher and higher levels.

[TBD] [approximate table based on ramp and amperage measurements]

Source Code

The source code is the same as the Emisar D4, available from Intl-Outdoor’s D4 page:

He links to a zip file with the D4’s current code in it.

I also host the code in my repository and created a new D4-specific branch which will only contain stable releases:

Within both of those, you probably want to click “Browse the code”, “Tom_E”, then “RampingIOS”.

Potential Issues

The driver has reverse polarity protection, but I’ve seen two reports (for the D4) that it can hurt the battery. Don’t put the battery in backward, or it might get the light hot and permanently kill the battery.

The big-head proportions make clips a bit awkward, so it’s probably best used without a clip.

The driver seems to use about 4.5mA even without the LEDs on, so the absolute longest it could possibly run is about 28 days on a 3000 mAh cell. This can be improved significantly by using different firmware though. However, note that this only matters when the light is on, like at moon mode. Standby time (with the light off) is virtually unlimited.

The new rough texture feels nice but it’s probably easier to scratch. This is an unavoidable side effect of making it more grippy. I haven’t actually managed to scratch it yet, but I’ve been pretty gentle with it.

Upgrade Options

The D1 and D1S don’t really need upgrades, since the stock form is already pretty optimized. However, it’s compatible with some open-source firmware if anyone wants to change the interface:

  • RampingIOS v1
  • RampingIOS v2
  • Narsil
  • All current FSM-based interfaces, including Anduril, Baton, DarkHorse, etc.

One could also increase the throw by replacing the emitter with a dedomed XP-G2 or an Oslon Black Flat. It would make the hotspot significantly smaller though, and would decrease lumens significantly too.

Which one is best?

The Emisar lights offer a range of beam types…

  • D4: ~4 cd / lm (floody)
  • D1: ~32 cd / lm (throwy)
  • D1S: ~95 cd / lm (very throwy)

Which one is best depends on what you’re doing. Some traits which might matter are:

  • Physical size: the D4 is the smallest, but the D1 is pretty small too.
  • Clip use: The D4 works pretty well with a clip. The D1 and D1S are generally better without one.
  • Lumens: If you want to ceiling-bounce lots of lumens, the D4 puts out by far the most.
  • Up-close use: The D4 is the only floody option for up-close use.
  • Throw: If you need to see far away, the D1S goes a lot farther than the others.
  • Thermal performance: The D1S can run on turbo indefinitely, while the D1 needs to step down after a while… and the D4 steps down rather a lot very quickly.
  • Choice of battery type: The D4 and D1 both have other tubes available. The D1S does not.
  • Balance: The D1 is a nice middle ground between flood and throw.

For example, let’s say you want to see something 50 meters away, and need it to be illuminated to about 4 candelas. All the Emisar lights so far can do it, but with very different power levels and runtimes:

  • D4 XP-G2: 16-17 A, 10-12 minutes
  • D4 XP-L HI: 9.5 A, 19 minutes
  • D1: 1.4 A, 2.1 hours
  • D1S: 0.46 A, 6.5 hours

In general, I use my D4 the most. This is because it’s the smallest, and because most of my needs are indoors. But I tend to carry a D1 shorty in my purse too, because it’s a convenient small size and lets me see a lot farther when I need to. The D1S is great, but I generally leave it at home unless I’m expecting to need a thrower. It’s small for what it does, but still big enough that I don’t carry it by default.


What I liked:

  • Unusually good throw for its size, for both lights.
  • Same UI as the groundbreaking Emisar D4, with smooth ramping, shortcuts to min/max/mem, and a few extras.
  • Hosts have a high-quality feel with solid components, decent anodizing, square threads, etc.
  • Hosts are unusually small for what they do… they obsoleted some of my other lights.
  • Available in neutral white.
  • Open-source code means it can be customized extensively.
  • The D1 offers a choice of three tube lengths and battery types.
  • Square threads on the body tube.
  • Although the lens has a clearly visible anti-reflective coating, it doesn’t make a blue halo or a green beam. It’s some kind of AR that I haven’t really seen before.
  • Uses the same awesome springs as the D4.
  • The D1 handles heat a lot better than the D4, and the D1S even more so. The D1S probably doesn’t even need thermal regulation, because in my testing it never got too hot even when running at full turbo.

Things I feel neutral about:

  • The grainy D1S anodizing is more grippy (feels more like unpolished stone, less like metal), but it also picks up scuff marks relatively easily. These marks seem to wipe off though. It feels a bit like bead-blasted titanium, for anyone who has touched that kind of material, only harder and more velvety.
  • Long protected cells do not fit. I tried a Panasonic NCR18650A with protection (69.5 mm), and the tail cap would not tighten. It stopped with the O-ring still exposed. This didn’t matter on the D4, since a protected cell wouldn’t handle the amps anyway, but it’s a bit more relevant for the D1 / D1S due to their reduced power needs.
  • The tail spring PCB appears to be press-fit or glued.
  • The driver is glued in. Fortunately, it wasn’t very hard to pop out from the inside.

What I didn’t like:

  • No short tube for the D1S. It looks ridiculous, but the balance is surprisingly okay in shorty form… and runtime is pretty okay too, with an Aspire cell.

_the_ End

(reserved for tear-down, pics of internals)

Nice review! I just got my D1 yesterday. But I know I need a D4 but I don’t know to replace my UT02 with the D1S or not. I want to reduce my flashlight quantity and I became a big fan of side E-switch form with ramping firmware since my Q8 came to me :smiley:

Please make some outdoor beamshots with the D1 and D1S!

D1s specs super close to the u21/ut02.
Its best ui vs best design (26650, better look). Only my opinion.

Woo my persistence pays off thanks for the review

Great review, thanks!

Nice review!
I’m not really a fan of the looks of both the D1 and D1S, but further they are great flashlights!

Damnit, I need a D1. I already I have two throwers, which have a specific and infrequent purpose. I really don’t need this. But I need it.

Great review ToyKeeper, thanks! :smiley:

Best UI ?
Is a ramping UI the best for a thrower when you only using it in high or turbo modes ?

Thanks for the review! This light is begging for a lanyard attachment point.

Great review. If the lumens and throw aren’t that much different and the battery tubes aren’t compatible with the D1/D4 I probably won’t buy this light. Give us a bigger battery and at least twice the throw and I will jump on it!

Lumens are about the same. Lux goes from 40 to 124 kcd with the bigger head.

Thanks for another well-written review, TK! :+1:

I love the D4 and D1, and I’m chomping at the bit for a D1S.

Looking forward to your D7 review! :partying_face:

Thanks for the review, can we get some weights for the two torches?

Thanks for the review. The D1S looks like a C8 on steroids!

Do you use it in high and turbo only?
I do mostly on low-medium.
Anyway, I guess Emisar ramping is not perfect for you. You’d be better off with a ramping UI that starts high and goes up from there.

Thanks for the review!
I just sold my C8 and i would love to get D1S
Anyone knows when D1S hits the market?

Dubble click for turbo and ramp down if needed. Seems ok for your use.

Thanks for the review TK. Still in doubt if I need one.

I have not doubt that I need one gray D1S….D1 and D4 will be angry if I not bought his big friend…
I hope Hank list this soon in his store!!