BenQ ScreenBar Halo 2: Data check on the monitor light bar

Suits you if: The Halo 2 is not a general desk lamp but a light for the top edge of a monitor. Two things therefore decide the purchase: whether the clamp fits your screen and whether your power adaptor supplies the required 5 volts at 3 amps, because BenQ gives 15 watts as the maximum power consumption, and a weak USB port on the monitor is not sufficient for that on paper. According to the manufacturer, the colour rendering of the front light is Ra 95 or higher, and the colour temperature can be set between 2,700 and 6,500 kelvin. The manufacturer's page gives no luminous flux in lumens, so neither an energy efficiency class nor a comparison with a desk lamp by lumens can be calculated cleanly. For work on paper in changing positions, a classic lamp remains more flexible.

What the documents confirm

On its own specification page, BenQ describes the ScreenBar Halo 2 as a monitor light bar with a dual colour LED for front and back light. According to the manufacturer, the front light reaches a colour rendering index of Ra 95 or higher and a colour fidelity Rf of 96 or higher. Ra and Rf are two figures for the same question: how natural colours look under this light. Both figures expressly apply to the front light; the page gives no value for the back light.

The mechanical details are more complete than for many competing models. According to the manufacturer, the lamp measures 50 by 14.3 by 10.9 centimetres and weighs 0.8 kilograms net, and the controller measures 7.4 by 7.4 by 3.95 centimetres. The USB cable is 150 centimetres long. The clamp holds flat and curved monitors with a thickness of 0.43 to 6 centimetres, and according to BenQ a webcam accessory is included.

The key data according to the manufacturer at a glance:

Feature	Figure according to BenQ	Source
Light source	Dual Color LED	Specification page
Colour rendering, front light	Ra 95 or higher, Rf 96 or higher	Specification page
Colour temperature	2,700 to 6,500 kelvin, continuously adjustable	Listing (seller's statement)
Central illuminance	over 1,000 lux at a height of 50 cm	Specification page
Area at 500 lux	85 by 50 cm	Specification page
Power input	5 V, maximum 3 A, USB Type-C	Specification page
Power consumption	maximum 15 watts	Specification page
Monitor thickness at the clamp	0.43 to 6 cm, flat or curved	Specification page
Controller	cordless, rechargeable battery, up to three months	Product page

The compatibility figure is the core of the purchase decision and is consistent between the manufacturer's page and the listing: 0.43 to 6 centimetres thickness at the clamp point. The listing adds a curvature of 1000R to 1800R. This additional figure appears only in the listing, not on the specification page we read, and is therefore a seller's statement.

The luminous flux in lumens is missing entirely from the specification page. Instead, BenQ gives illuminance in lux on the work surface. That is usual for monitor light bars, because the light is directed asymmetrically onto the desk rather than into the room. But it also means that a lumens-per-watt calculation, as you know it from room lights, is not possible from the manufacturer's documents.

The power supply: 15 watts is more than many monitor ports supply

The power input is given as 5 volts at a maximum of 3 amps. Calculation: 5 volts times 3 amps gives 15 watts, and BenQ gives exactly these 15 watts as the maximum power consumption. The figure is consistent in itself, so it describes a lamp that at full output genuinely needs a power adaptor with 15 watts at the USB-C output.

This raises a question that buyers often overlook: where does the power come from? Under the usual specification, a USB 2.0 port supplies 5 volts at 0.5 amps, that is 2.5 watts, and a USB 3.x port supplies 5 volts at 0.9 amps, that is 4.5 watts. These two values come from the general USB specification and not from a BenQ document. If you connect the lamp to such a port on a monitor or laptop, only 17 to 30 per cent of the 15 watts is available to it on paper (2.5 divided by 15 gives 0.17, 4.5 divided by 15 gives 0.30). Whether the lamp then shines only dimly, switches off or does not start at all is not described by BenQ.

In practice, this means: plan for a USB-C power adaptor with at least 5 volts and 3 amps. A modern charger of the kind sold for smartphones or laptops usually meets this. Whether BenQ includes a power adaptor is not clearly stated on the pages we read. Check the contents of the package in the listing before buying.

Running costs stay low even in the least favourable case. Calculation: 15 watts times 8 hours gives 120 watt hours, that is 0.12 kilowatt hours per day. Over 220 working days, that is 26.4 kilowatt hours per year. At an assumed electricity price of 35 cents per kilowatt hour (an example value, not a tariff), that would be around 9.24 euros. Because the lamp usually runs dimmed in daily use, the real figure is lower. The article LED power consumption and costs explains more.

The clamp: dimensions, cameras and curvature

The clamp is the second point where the purchase can fail. BenQ gives a monitor thickness of 0.43 to 6 centimetres, that is 4.3 to 60 millimetres. Measure the thickness of your monitor at the top edge, not at the thickest point of the stand. Many modern flat screens are only a few millimetres thick at the top edge, in which case the value is close to the lower limit. For monitors with a strongly contoured back, for example with a vent housing at the top, the upper limit may be exceeded.

The lamp is 50 centimetres wide. The width of a 16:9 monitor follows from the diagonal: diagonal in inches times 2.54 times 0.872. That gives about 53 centimetres at 24 inches, 60 centimetres at 27 inches and 71 centimetres at 32 inches. The lamp therefore covers almost the whole width at 24 inches, while at 27 and 32 inches there is room left and right. On a 34-inch ultrawide with a width of about 80 centimetres, it is clearly narrower than the monitor.

For curved monitors, an approximation applies: the rise of a circular arc is the width squared divided by eight times the radius. For the lamp's 50 centimetres and a radius of 1,000 millimetres (1000R), this gives 500 times 500 divided by 8,000, so roughly 31 millimetres. At 1800R it is 250,000 divided by 14,400, so roughly 17 millimetres. This is a worked example, not a manufacturer's figure. It shows that with strong curvature the clamp grips only in the middle and the ends of the lamp deviate from the monitor surface. How the mount compensates for this is not explained on the manufacturer's page.

The webcam check remains the most important step. If a camera or sensor sits on the top edge, the clamp may cover it. According to the specification, BenQ includes a webcam accessory, but the page does not explain which cameras it suits. The listing claims that the lamp fits without covering webcams. That is a seller's statement that you must verify on your own monitor with a built-in camera.

Light and operation: what the figures say

BenQ gives the central illuminance as over 1,000 lux at a height of 50 centimetres. At 500 lux, the manufacturer gives an illuminated area of 85 by 50 centimetres, that is 4,250 square centimetres or 0.425 square metres. Calculation: illuminance times area gives the luminous flux that arrives on the area at a minimum. 500 lux times 0.425 square metres gives about 212 lumens. This is a lower limit for the luminous flux on the writing surface, not the luminous flux of the lamp itself, because scatter and light emitted backwards are not included.

BenQ describes the 18 degree deflection angle as a measure against reflections on the screen. According to the manufacturer's page, the reflector consists of eight segments with twelve precision lenses. This is a design detail. How strong glare and reflection are on your monitor depends on the panel surface, seating distance and lamp position, and no measurement is available on this. We have not measured anything and did not have the lamp in hand.

According to the listing, the colour temperature can be set from 2,700 to 6,500 kelvin. 2,700 kelvin corresponds to warm white incandescent light, 6,500 kelvin to cool daylight. Which setting suits which time of day is explained in the article Colour temperature and kelvin. What matters: the figures for Ra and Rf apply to the front light, not separately to each individual kelvin value.

Control is by a cordless controller with a rechargeable battery and a USB-C charging socket. According to BenQ, the battery lasts up to three months, and the listing says the same. The page does not say what this duration depends on. A controller with a battery is one more device that has to be charged now and then. There is also an ultrasonic sensor that detects movement at a distance of about 60 centimetres in front of the monitor and switches the lamp off after five minutes without detected activity. If you sit still in front of the screen for a long time, for example when reading, you should find out whether this automatic function can be switched off. The documents we read say nothing on this.

On the subject of flicker, the specification page gives no value in the sections we read. How to recognise flicker in a lamp is explained in the article LED flickers.

A second look: registration and energy efficiency

For light sources, Regulation (EU) 2019/2015 requires an energy label and registration in the EU product register EPREL. We queried the register for the supplier BenQ. It returns 16 records from BenQ Europe B.V., named after model identifiers such as CR25, CR26, CR21 and CR23, some of them separate for front and back light. No identifier carries the name ScreenBar Halo 2, and BenQ does not state the identifier of the Halo 2 on the pages we read.

We deliberately did not match one record. The entry CR25 Light source-Front states 2,500 lumens at 21 watts in class E. According to the specification, the Halo 2 has a maximum of 15 watts, so a record with 21 watts cannot describe the same light source unless BenQ shows otherwise. We therefore do not state a class for the Halo 2. The BenQ records mostly carry the attributes NMLS (not connected directly to the mains) and NDLS (non-directional), which is to be expected for a lamp on a USB port. If a matching record existed, the factor 0.926 would apply under Annex II of the regulation for non-directional light sources without direct mains connection. Without luminous flux and without a record, this remains an open calculation.

What this means for you: an energy label should be visible on the packaging or in the listing. Ask BenQ for the identifier if you want to check the class.

What no source answers

Several questions that matter for the purchase cannot be resolved with the documents. We name them rather than guess.

Luminous flux in lumens: The manufacturer's page gives only lux on the work surface. The 15 watts are the maximum value; a ratio of lumens to watts is not documented.
Behaviour with a power source that is too weak: What happens if the lamp is connected to 2.5 or 4.5 watts is not documented.
Flicker-free operation and blue light: The sections we read give no certification or standard for this.
Durability: Rated lifetime in hours and guarantee period do not appear in the sections we read, so we give none here.
Clamp behaviour on unusual rear housings: Whether the mount grips securely on housings with ribs, vent slots or strong curvature is not described.
Reflections on glossy panels: How well the 18 degree deflection angle prevents reflections has not been measured.

There is also a limitation regarding the sources: the manufacturer's pages are BenQ's own presentation. They are the right source for dimensions and connection values, but they come without independent measurement. Claims about eye comfort or concentration that marketing builds around this lamp are not supported by the documents. For a general overview of whether a monitor light bar makes sense for you, see the article Are monitor light bars worth it?, and for visual comfort see the article working in an eye-friendly way.

Who the Halo 2 suits and who it does not

The Halo 2 suits you if your monitor has a suitable top edge, you want to save desk space and you want to direct the light at the work area in front of the screen. That includes having a USB-C power adaptor with at least 15 watts nearby and being willing to charge a small controller now and then. The back light, which brightens the wall behind the monitor, is a distinct feature of the Halo range. According to the seller, it reduces the brightness difference between the screen and the surroundings.

It suits you less if you write on paper a lot, draw or work in changing places. The light is aimed at the area directly in front of the monitor. An adjustable clamp lamp or floor lamp can be positioned better over a sheet of paper. It also does not suit you if a camera or sensor sits on the top edge and the included webcam solution does not fit your model, or if your monitor is thicker than 6 centimetres at the clamp point.

If you want to compare alternatives before buying, the page BenQ ScreenBar alternatives lists further monitor light bars with their documents. General selection criteria for workplace lamps are in the guide Choosing a desk lamp. How much light your workplace needs overall is answered by the lighting calculator. For a sense of the price band: the Halo 2 sits in the upper range of monitor light bars, and whether that is worthwhile depends on the design rather than on a documented amount of light. Light therapy does not replace medical treatment.

Sources and transparency

This page is built from documents, not from our own laboratory. Below are all the sources that were opened for it, and next to them, explicitly, every statement that is our own calculation or interpretation.

Sources checked

Our own calculation, interpretation or matching

The spare power at USB 2.0 and USB 3.x ports (2.5 and 4.5 watts) comes from the general USB specification and not from a BenQ document; the percentage calculation based on it is our own calculation.
The width of 16:9 monitors from the diagonal, the rise of the arc on curved monitors and the running costs at an assumed price of 35 cents per kilowatt hour are our own calculations, not manufacturer's figures.
The conversion of 500 lux over 0.425 square metres to roughly 212 lumens is a calculated minimum value on the surface and not a statement of the lamp's luminous flux.
The decision not to match the EPREL records rests on comparing 21 watts with 15 watts and is an interpretation, not a confirmation by BenQ.

What remains open

The luminous flux in lumens is not given in the manufacturer documents we read, so neither a luminous efficacy nor an energy efficiency class can be calculated for the Halo 2.
The EPREL model identifier of the Halo 2 is unknown. The BenQ records cannot be matched unambiguously on the data we read; the record CR25 Front states 21 watts against a 15 watt maximum according to the specification.
The behaviour of the lamp on a USB port with only 2.5 or 4.5 watts is not documented, nor is whether a power adaptor is included in the package.
Flicker-free operation, a blue light standard, rated lifetime and guarantee period did not appear in the sections of the manufacturer's pages we read and are therefore not stated.
The curvature figure 1000R to 1800R and the colour temperature range come from the listing and are not reproduced on the specification page we read.

Checked and not reachable

https://www.benq.eu/de-de/lighting/monitor-light/screenbar-halo-2/faq.html: responds with HTTP 404, the path does not exist at this address.