Among flashlight enthusiasts, flashlights with a zoom function (also called “zoomies”) are considered almost synonymous with poor quality and weak performance. This is partly because a large proportion of the poorly made and overpriced models on the market are zoom flashlights. Another reason is that the design of these flashlights comes with inherent drawbacks that limit their performance. However, it doesn’t have to be that way.
As an alternative to traditional zoom flashlights, there are models with multiple LEDs behind different optics or flashlights with attachable diffusers. In addition, there are innovative technologies like the one used in the Imalent BTL50 that allow the beam to be adjusted without any moving parts.
You can find the German version of this review on my website: SammysHP Blog › Imalent BTL50
The flashlight was provided by the manufacturer for this review. Thank you very much!
Overview and hardware
The BTL50 comes in a sturdy box with a magnetic closure. The flashlight is secured in a foam insert and the accessories are packed in a small box.
- Lanyard
- USB-C charging cable
- Manual (EN, ZH, DE, IT, AR, JA, FA, KO, TH, FR, VI, BG, RU, ES)
Overall, the user manual is easy to understand. However, the different language versions do not appear to be up to date with one another. For example, the German translation refers to a “continuous adjustment from spotlight to floodlight”, while the English version instead states that it “allows for 4 levels adjustment of the spotlight and floodlight”.
The design of the BTL50 stands out noticeably from that of many other flashlights and may have been inspired by the appearance of a night vision device. The upper half of the cylindrical body is covered with a leather-like material that provides both a visual and tactile contrast to the matte black anodized aluminum.
This covering is available in four colors: black, blue, gray and gold. On my “gold” sample, the color appears slightly different depending on the lighting, but in every case it differs noticeably from the product photos.
On its own, the BTL50 is a fairly compact flashlight, although it is somewhat on the thick side. Weighing just under 250 g, it has a reasonable heft that is definitely noticeable. As an everyday carry flashlight, it is only suitable to a limited extent, but it fits easily into a jacket pocket.
Length: 110 mm
Diameter: 35 – 38 mm
Weight: 239 g
However, when you take the size of the built-in battery into account, the flashlight appears in a different light. With a capacity of only 3000 mAh, the battery is comparable to a typical 18650 cell. Given the size of the BTL50, however, you would expect a 21700 battery with a capacity of around 5000 mAh.
In my opinion, the aluminum bezel also does not provide enough protection for an everyday carry flashlight. It extends only about one millimeter beyond the lens, leaving it relatively vulnerable to scratches and making it more likely to break if the flashlight is dropped. However, I don’t see this as a major drawback. The BTL50 is primarily aimed at users who value its technical capabilities and are likely to handle it with appropriate care. After all, even a smartphone usually makes it through everyday use without damage.
The flashlight is operated using a rotary switch and a button on the tail. A status LED is also located there. Overall, the flashlight features a very cohesive, slightly futuristic and elegant design.
On the flattened underside, there are three raised areas that look like buttons and reinforce the flashlight’s resemblance to a night vision device. Beyond that, they serve no purpose. This is a missed opportunity, as this area would have been ideal for integrating a clip.
The only attachment option is two holes at the rear of the flashlight that allow a lanyard to be threaded through. This would allow you to wear the BTL50 around your neck, for example. A matching belt holster would have been a nice addition.
The BTL50 features a built-in Li-ion battery with a capacity of 3000 mAh. It can be charged via a USB-C port on the flattened side.
The port is protected against water and dirt by a silicone cover. It is easy to open and close, yet stays securely in place when closed. Since it sits flush with the housing, accidental opening is unlikely.
With a 5 V USB power supply, the current reached up to 2.75 A in my tests, while around 1.4 A was achieved at 9 V. (According to the user manual, up to 12 V is even possible. The maximum charging current at the battery is supposed to be 4.8 A.) In both cases, the battery is fully charged again after just over an hour. The charging progress is indicated by the status LED next to the button: it flashes red while charging and changes to green when the battery is fully charged. When the charging cable is connected, the flashlight switches off automatically and cannot be used while charging.
According to the manufacturer, the BTL50 has an IP56 rating. This means it is protected against “powerful water jets”, which in practice usually means “can also be used in the rain”. The flashlight should definitely not be submerged in water. It is also supposed to withstand drops from a height of up to half a meter. Earlier versions of the user manual listed an IP68 rating and a maximum drop height of one meter.
User interface
The BTL50 is operated using a button and a rotary switch at the tail of the flashlight. The button is used to turn the flashlight on and off as well as to adjust the brightness. Due to its only slightly pronounced, somewhat mushy actuation point, the button provides relatively little tactile feedback.
The width of the beam is adjusted using the rotary switch. It clicks gently into place at four positions. The position is detected using Hall sensors, meaning a strong magnet can temporarily interfere with its operation.
The UI is straightforward and contains no surprises. In fact, I would have liked to see some additional features, such as direct access to the lowest level by holding down the button or momentary operation when the lockout is enabled.
| State | Action | Function |
|---|---|---|
| Off | 1 click | Turn on (previously used brightness) |
| Off | 2 clicks | Turbo |
| Off | 3 clicks | Lockout |
| On | 1 click | Turn off |
| On | 2 clicks | Turbo |
| On | Hold | Change brightness (Eco → Low → Mid → High) |
| Turbo | 1 click | Turn off |
| Turbo | 2 clicks | Strobe |
| Lockout | 3 click | Unlock |
Basically, everything was done right here. The only thing I find annoying is that the low brightness level can only be reached after cycling through all the brighter levels first (which takes a few seconds). The strobe mode with a frequency of 10 Hz is hidden behind Turbo and cannot be accessed directly.
When the flashlight is switched on, a status LED indicates the approximate charge level of the battery. However, it remains green most of the time. Only when the battery voltage reaches 3 V (according to the user manual), it starts flashing red. One or two intermediate levels would have been a nice addition.
The flashlight is best used in a “tactical grip”. The thumb rests on the button, allowing immediate access to the controls at all times. Users with small hands may have difficulty holding the flashlight securely due to its large diameter.
Both the button and the rotary switch can be operated comfortably with the thumb. Unfortunately, the rotary switch on my first BTL50 was defective and repeatedly jammed during normal use. Imalent promptly replaced the flashlight for me and the switch on the new unit works flawlessly.
A major drawback is that the front and rear ends are barely distinguishable from each other. This means there is a good chance of picking up the flashlight the wrong way around and leaving only a fingerprint on the lens instead of turning the flashlight on.
Illumination
Although the manufacturer does not provide any specific information about the LED model used, a look through the lens suggests that a Luminus SFT-42R is likely being used. This is indicated in particular by the round light emitting area and the characteristic arrangement of the bond wires.
The actual highlight of the BTL50 is its electronic zoom or diffusion technology. The light from the LED is first focused by an aspheric lens and then passes through a liquid crystal layer. This layer acts as a diffuser and scatters the light, with the degree of diffusion being electronically adjustable. This allows the width of the beam to be adapted to the particular situation.
The intense coloration of the anti-reflective coating on the protective glass and apparently also on the lens behind it is particularly noticeable. Depending on the viewing angle, it appears in shades of magenta, cyan and blue.
The cool white light has a color temperature of around 6000 K. A slight yellow tint is visible in the center, while the edge appears noticeably more bluish. Color rendering is mediocre but adequate. Replacing the LED would likely be rather difficult due to the complex construction.
The “zoom” works exceptionally well in practice. It is not only convincing in terms of practical usefulness, but is also simply a lot of fun to use. However, at its maximum setting, I would have liked the effect to be a bit more pronounced.
On my usual test area, the difference in range is easy to see. The more focused the beam becomes, the greater its range.
As the beam becomes more focused, the amount of spill also decreases. This can be beneficial in certain situations, for example when there are bright objects in the foreground. At the same time, the reduced illumination of the surroundings can also be a disadvantage and make orientation more difficult.
Whether such a zoom function is actually necessary ultimately depends on the intended use. In most cases, a fixed beam is likely perfectly sufficient. Alternatively, combining multiple flashlights can also make sense, such as a floody headlamp and a more tightly focused handheld flashlight. Regardless, the integrated diffuser of the BTL50 is a nice gimmick that also offers some practical applications.
Driver and runtime
The manufacturer does not provide specific details about the type of driver used, but advertises it as a “high efficiency constant current circuit” that will maintain constant brightness.
| Mode | Brightness¹ | Runtime¹ | Intensity¹ (Throw²) |
|---|---|---|---|
| Turbo | 3000 / 1000 lm | 1.5 min + 1:14 h | 124 270 – 24 500 cd (705 – 313 m) |
| High | 1000 lm | 1:24 h | 47 790 – 13 806 cd (437 – 235 m) |
| Medium | 550 lm | 2:48 h | 25 665 – 7 960 cd (320 – 178 m) |
| Low | 250 lm | 5:22 h | 13 275 – 5 310 cd (230 – 146 m) |
| Eco | 15 lm | 89 h | 27 – 17 cd (10 – 8 m) |
¹ According to manufacturer ² ANSI FL1
The flashlight impresses in the runtime test with excellent regulation and maintains a constant brightness level throughout the entire runtime. The runtimes specified by the manufacturer are achieved in testing and are even exceeded in some cases.
The only exception is Turbo mode, although the manufacturer explicitly points this out. A temperature monitoring system prevents the flashlight from overheating. With slight cooling, the maximum brightness is maintained for three minutes, which is twice as long as specified in the manual.
The thermal images show an even distribution of heat. The solid aluminum body likely contributes to this as well. In the uncooled test, the surface reaches a temperature of around 50 °C, at which point the flashlight feels hot but can still be held.
Thermal images with Zoyi ZT-R02
All brightness levels are regulated without PWM and no ripple could be detected with the oscilloscope either. Due to the built-in battery, it was not possible to measure the current, and the voltage at which the flashlight switches off to protect the battery from over-discharge could not be determined either.
Conclusion
The Imalent BTL50 is not a zoom flashlight in the traditional sense, yet the width of its beam can still be adjusted – without any moving parts. This is made possible by an integrated diffuser whose strength can be controlled electronically. This technology is extremely rare in flashlights, but highly practical.
Although the flashlight feels compact and comfortable to handle, the capacity of the built-in battery is somewhat limited for its size. The flashlight stands out with its slightly futuristic design and stylish leather-like covering. The width of the beam is adjusted with a rotary control, which allows for smooth, intuitive operation. A pocket clip or holster, however, would have been a welcome addition.
Got curious? The Imalent BTL50 can be ordered here at imalentstore.com.