Emisar D4 (V2)
This is the updated 2019 version of the Emisar D4, produced by Hank Wang of Intl-Outdoor.
Disclaimer: I helped make this. I’m not an impartial reviewer. This thread is primarily intended to answer everyone’s questions about this brand new product.
I reviewed the original Emisar D4 too, if you’d like more pictures, information, and background context about this light.
What’s New?
If you’re already familiar with the original D4 and just want to know what changed, here’s a quick run-down.
Compared to the original D4 with RampingIOS, the new D4V2 is updated in these ways…
- Added an optional steel bezel
- Added an optional tailcap magnet
- Added a tailcap lanyard attachment point
- More grip on the battery tube
- Different host colors available
- More LED types and tints available
- MCPCB is screwed down now
- Larger MCPCB with dedicated screws holes, so the 4 optic legs are in intact in the D4V2
- Rotated the LEDs for a smoother beam
- Added aux LEDs with 7 configurable colors plus rainbow and voltage modes
- Upgraded the driver to use a new MCU with more pins and twice as much space
- Added spring-side firmware flashing pads to the driver, for easier updates
- Fixed reverse polarity protection
- Completely new firmware — Anduril instead of RampingIOS… so it has a lot more modes and options. More details on this below, since it’s too much to cover in this quick summary.
So it’s more or less the same D4 people have loved for the last two years… only better.
Official Specs
Battery type: Unprotected, high drain batteries only, protected cells won’t work
Aux LEDs: Red, yellow, green, cyan, blue,magenta, rainbow aux LED options is selectable through config UI, as well as the voltage indication function.
Features:
- CNC machined from aircraft-grade aluminium
- Efficient UK made Carclo Quad LED optics
- Anti-reflective coated glass lens
- Unihead construction
- High lumen output and low moon output
- Ramping interface
- Electronic soft touch switch
- 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: 95mm(length) * 28mm(head) * 24mm(body), 80mm(lenght 18500), 63.5mm(lenght 18350)
OTF lumen output at start-up
- XP-G2 S4 : 3300lm
- Nichia 219C : 3000lm
- XP-L HI : 4300lm
- SST-20 6500K : 4200lm
- SST-20 5000K : 4200lm
- SST-20 4000K/3000K 95CRI : 3000lm
Measurements
Output:
- Beam type: Hotspot plus corona, narrow spot or floody depending on the optic chosen
- Power: As much as your battery can push (probably around ~15 A)
- LEDs: Cree XP-L HI, Nichia 219C, or Luminus SST-20
- Brightness ~0.2 lm at bottom of ramp, ~2500 lm to ~4500 lm at top of ramp depending on LED type and battery, plus a smooth ramp between
Dimensions:
- Length: 95.2 mm
- Bezel diameter: 28.0 mm
- Head diameter: 30.2 mm diagonal
- Body diameter: 24.0 mm
- Clip groove diameter: 22.6 mm
- Lens: 25.6 x 1.5 mm
- Driver: 21.9 mm diameter, 1.7 mm thick PCB, 3.3 mm w/ components
- Maximum cell length: 67 mm (protected cells won’t fit)
Host / Build:
- Weight: 73.9 g w/ steel bezel and magnet tailcap, 119.6 g w/ battery
- Switch type: Momentary / electronic side switch
- Body material: Hard anodized aluminum: black, grey, or sand (maybe other colors later too)
- Lens: Glass
- Anti-roll and tail-stands nicely
- Waterproof to IP67 (1m underwater) (from specs, not measured)
- Premium BeCu (Beryllium Copper) springs capable of high current without sagging
- Optic: Carclo 10622 / 10623
Electrical:
- Driver type: FET+1 (regulated up to 350mA or ~140 lm, hybrid direct drive at higher power levels)
- Operating voltage: 2.8V to 4.35V
- Battery: One 18650, 18500, or 18350 cell (with matching tube)
- Parasitic drain:
- ~0.02 mA with aux LEDs off (17 years to drain a 3000mAh cell)
- ~0.06 to ~0.12 mA with aux LEDs on low mode (2.5 to 6 years)
- TBD mA with aux LEDs on high mode (my sample has different resistors, so I can’t measure)
- (probably about ~0.2 to ~0.4 mA on blinky mode, or 1 to 2 years runtime)
- (probably about ~3 mA on high mode, or about 50 days runtime)
- Low-voltage protection: Yes
- Thermal protection: Yes
- Reverse polarity protection: Yes
- Power can be locked out by loosening the tailcap, or by entering a lock-out code on the button
MSRP: $45 USD
Interface
TL;DR: Click for on/off, hold to change brightness. That’s all you really need to know to use this UI.
Beyond that, the user interface (UI) has … a lot of features / functions. There’s a good chance that, if you want a specific thing, there’s probably a way to do it. I’d suggest reading the manual for general info about how it works, or referring to the UI diagram below. Or both.
If it helps, here’s a partial list of what changed in the UI between the original D4 and D4V2:
- Instead of just smooth ramping, there is also a stepped ramp with discrete levels… and switching between the two is quick and easy
- Both ramps have configurable floor and ceiling levels, and the user can choose how many steps in the stepped ramp
- Made ramp direction predictable, and added a shortcut to ramp down
- Added an option to choose between automatic or manual memory to choose the brightness at single-click from off (automatic uses the last-ramped level, manual uses a level the user explicitly configured)
- Made moon mode lower, and dramatically increased moon mode runtime
- Added more modes behind the battery check mode: Sunset, Beacon, and Temperature Check
- Moved Lockout mode from 6 clicks to 4 clicks for faster access
- Made Lockout mode double as a momentary moon mode with 2 levels of output, so it doesn’t need to be unlocked for quick tasks
- Made confirmation blinks much faster
- Added a “Muggle Mode” on 6 clicks, to make the light safe when lending it to other people (is limited to only safe levels, and all other modes are inaccessible)
- Moved Beacon mode into the battcheck mode group, and made its blink shorter
- Made Beacon Mode’s timing and brightness configurable
- Much smoother thermal regulation
- Changed thermal config from “hold until hot” to a sensor calibration step plus an explicit temperature the user can enter precisely
- Added support for colorful aux LEDs
- Added an entire group of strobe / ambient modes: adjustable Party Strobe, adjustable Tactical Strobe, adjustable Bike Flasher, Lightning Storm mode, and adjustable Candle Mode with configurable self-shutoff timer
- Made Momentary Mode brightness configurable
- Made Momentary Mode work with strobe-group modes too, for momentary strobes (good for light painting)
The new firmware is a complete from-scratch rewrite, but the basic usage is the same: Click for on/off, hold to change brightness. That’s all you really need to know to use it.
Aux LEDs
The aux LEDs turn on during the “off” and “lockout” modes. They are off in other modes, like when the main LEDs are on.
This animation shows frames from a video while the light is in “rainbow” mode:
The rainbow mode looks exactly like this animation; it doesn’t fade between colors because that would require keeping the MCU awake, and that would greatly reduce the standby time.
The aux LEDs have four brightness levels (modes) and nine colors.
Brightness levels / modes:
- Off
- Low
- High
- Blinking (1 Hz low/high pattern)
Colors:
- Red
- Yellow
- Green
- Cyan
- Blue
- Purple
- White (ish)
- Rainbow animation
- Voltage (blue = good charge, green = medium charge, red = low battery, off = critical battery)
These can be configured independently for the “off” mode and the “lockout” mode, so the user can tell at a glance whether the light is locked or just off.
To change the aux LED brightness level / mode:
- In “off” mode: Click 7 times.
- In “lockout” mode: Click 3 times.
To change the aux LED color:
- In “off” mode: Click 7 times, and hold the last click until the desired color is reached.
- In “lockout” mode: Click 3 times, and hold the last click until the desired color is reached.
The modes and colors are in the order shown above. Rainbow mode is indicated by cycling colors, while voltage mode is indicated by faster cycling colors.
Here’s how the MCPCB and aux LED board look. My sample has different resistors than the production version, but it should otherwise be the same.
I tried to measure aux LED power use. I can’t say for sure my numbers are good, since my D4v2 has the resistors set up differently than a production model, and my measuring equipment isn’t very precise at low power levels, but here’s what I got…
- Low mode (rainbow): 0.077 mA to 0.107 mA, depending on how I measure
Runtime: 3.7 to 5.2 years
- High mode (rainbow): 2.89 to 3.01 mA, depending on how I measure
Runtime: 48 to 50 days
- Blinky mode (rainbow): 0.205 to 0.424 mA, depending on how I measure
Runtime: 0.9 to 1.9 years
For comparison, here’s moon mode, the bottom of the ramp:
- Moon mode: ~1.8 mA
Runtime: ~81 days
These were each sampled over time and then averaged. The power source was set at 3.7V. Runtimes assume a 3500 mAh cell.
Packaging
The light comes in the same packaging as other Emisar lights, which is simple but very effective at keeping the light safe during shipping. It’s a cardboard box which is heavily padded inside. It could probably fall off a plane and not cause any harm to the light inside.
I … kinda forgot to take pictures of the packaging, but it looks identical to the original D4 packaging except it says D4V2 on it. Here’s how that looked in 2017:
Comparison to other lights
Emisar D4 (original) vs Emisar D4V2:
Emisar D18 vs Emisar D4v2:
Host, Components, and Build Quality
The D4V2 has an O-ring and square-cut threads on both ends. The battery tube has a square knurling pattern for grip, and recessed grooves for attaching a clip. The tailcap has grip ridges and a lanyard attachment point.
The button still sticks out like the original D4, which makes it easy to press.
The lanyard hole’s edges are chamfered to make sure it won’t cut through the lanyard string:
The driver has pads for flashing firmware, which makes it really easy to update… if you have a pogo pin adapter. Without the adapter though, it’s nigh-impossible because the attiny1634 MCU doesn’t fit a SOIC8 clip.
I would not recommend trying to remove the driver. It’s glued like the original D4, but more importantly, it has a lot of wires! Here’s how the top side looks in my early prototype, with its brain hanging out:
Tailcap Magnet
There’s a magnet in the tailcap, if you want one. It sticks to stuff. For example, a door clasp:
… or a coated wire shelf:
… or even a single screw hanging from a vibrating ceiling fan:
The magnet is not as strong as the D4S magnet. It’s not quite as “friendly”, so to speak. But it’ll still stick to pretty much anything solid and ferrous.
Beamshots, Output, and Runtime
… eventually! 
(sorry, trying to post this review quickly to answer people’s questions… and the questions aren’t about the beam… because people mostly already know what the beam and runtime are like)
Default configuration:
- Ramp segments:
- Level 1 to 65: AMC7135 chip only
- Level 66 to 149: AMC7135 + FET
- Level 150: FET only
- Smooth ramp: 1 to 120
- Stepped ramp: 10 to 120 in 7 steps: 10, 28, 46, 65, 83, 101, 120
Thermal regulation
Compared to the original D4, the thermal regulation is much smoother. It’s mostly not noticeable when it makes an adjustment during use. It’s also far less prone to jumping around, so when it finds an optimal level it pretty much just stays there. Here’s how it looked during the first 10 minutes in a recent test:
The numbers on this graph are very approximate. I don’t know what the actual peak output was; just the relative brightness throughout the test. I scaled the graph according to the official specs, minus an arbitrary correction factor since my battery is getting a bit old so it’s not as bright as it would be with a fresh cell.
Source Code
… will be released soon. I’ve been a bit busy.
This light runs Anduril, and is thus supported by the FSM UI toolkit. That means it’s pretty easy to run other interfaces if desired. If you can describe your desired interface in the form of a flowchart, you can probably make it run on the D4V2.
Potential Issues
First off… THIS LIGHT CAN START FIRES. You have been warned. Be careful. Lock the light while carrying it.
The second potential issue also relates to heat. Thermal regulation is difficult on such a hot light, so it may exceed the configured temperature limit for a little while when turbo is activated. Over time it settles back to a comfortable temperature, but in turbo mode it can get very hot in just a few seconds.
With the aux LEDs on high mode, I don’t know how much power is used on the production version. I couldn’t measure that, since my sample has different resistors and thus different aux LED power use.
The clip is a clip-on type, not a screw-on or ring-in type. So it may scratch the anodizing around the clip attachment point.
Upgrade / Mod Options
The most obvious ways to modify this light are:
- Change the optic. It uses a standard type, so you can swap in other compatible optics.
- Change the emitters / MCPCB. Intl-Outdoor and MtnElectronics both sell compatible parts, though only the Intl-Outdoor boards will screw down.
- Glow tape or tritium vials could be added, but it may be redundant due to the aux LEDs.
- Firmware changes. This is easy to do if you have a pogo pin adapter, but difficult otherwise.
Most of the changes people would be likely to make are available as options while ordering. For example, a clip, a tailcap magnet, different emitter types, and different optics.
Summary
What I liked:
- … phew. Almost everything, really. This light sets the standard for what a pocket rocket can be.
- The steel bezel is a nice upgrade.
- The clip is much better than the original D4 (which had none, and then had a kinda bad one, and then finally got a decent clip) (D4V2 uses the finally-decent version).
- Basically all the upgrades are very welcome improvements to the tried-and-true D4.
- I particularly like the firmware flashing pads, but I may be part of a pretty small population who cares about that.
- Many choices of emitter type and tint, to suit almost anyone’s taste.
- It ships with a full-featured version of the latest Anduril.
- Emisar laid new foundations for the next generation of flashlights, and that makes things better for all of us — even those who don’t actually buy the D4V2. When new tech shows up in other lights, it’s likely because of the work Emisar did.
Things I feel neutral about:
- Side switch still sticks out.
- The knurling feels a bit aggressive.
- Higher regulated modes would have been nice, but it’s not really a big deal.
What I didn’t like:
- I’m not a big fan of the sand/gold/tan color.
- On turbo, it gets hot very fast!
The End
Or an end, anyway.
. It will switch on in your pocket, you are obliged to lock it out which, however nice the user interface is, makes the handling medieval compared to my ancient EDC-tailclicky. If I need light, without looking or fiddling I have light in 1 second, when I’m done its back in my pocket in 1 second. That is how I have used my EDC for 8 years now (many times a day) and I see no reason to give that up for all the bells and whistles in the world.