Smartphone screens emit visible light that includes a blue-light component. But how much blue light can actually be measured when a phone is being used at close range?
We performed a simple measurement test using a smartphone and an AquaHorti light meter.
Short answer: under the test conditions shown in this video, the meter displayed 145 lux, 12 fc, a Blue Scale reading of 19.11%, approximately 0.1 W/m² irradiance, and a CCT of 5897 K.
These values describe the light measured in this particular setup. They do not by themselves determine whether the phone is safe or harmful to the eyes.
Watch the Original Smartphone Blue-Light Test
The original AquaHorti test video was published on March 27, 2025.
How Was the Smartphone Screen Tested?
The video first shows the smartphone being used normally.
The light sensor was then positioned near the face to simulate a close-range phone-viewing position while the screen remained on.
This type of setup can provide a practical snapshot of the light reaching the measurement point under those particular conditions.
However, the result depends strongly on factors such as screen brightness, displayed content, viewing distance, viewing angle, display mode and ambient lighting.
For a repeatable comparison, those variables should be kept as consistent as possible.
What Did the Meter Show?
In the simulated smartphone-use position shown in the video, the app displayed approximately:
| Measurement | Reading shown in the video |
|---|---|
| Illuminance | 145 lux |
| Foot-candles | 12 fc |
| Blue Scale | 19.11% |
| Irradiance (Ee) | 0.1 W/m² |
| CCT | 5897 K |
The spectrum preview also showed a visible blue-region peak together with the broader output from the phone display.
Test result
The smartphone screen produced a measurable blue-light component, but the measurement alone does not establish an eye-health risk.
Test Limitations
This was a practical demonstration rather than a standardized photobiological safety test. The video did not document a fixed measurement distance, calibrated screen-brightness setting, standardized screen content or controlled ambient-light condition. The readings should therefore be interpreted as measurements from this specific setup, not as universal values for smartphones.
That distinction is important.
What Does the Blue Scale Reading Mean?
The Blue Scale value is useful as a comparative lighting parameter.
For example, measurements can be compared when changing:
- screen brightness,
- display color mode,
- night mode,
- viewing distance,
- or different phones and displays.
A higher or lower percentage can show that the spectral balance has changed.
It should not be interpreted as a medical threshold or as a direct “safe / unsafe” score.
Does Blue Light From a Smartphone Damage Your Eyes?
A light meter cannot answer that question by itself.
It measures characteristics of the light reaching the sensor. It does not diagnose retinal damage, digital eye strain or any other medical condition.
The American Academy of Ophthalmology states that current evidence does not show a meaningful link between blue light from digital devices and damage to the human retina. Screen-related discomfort is more commonly associated with factors such as prolonged viewing and reduced blinking.
The International Commission on Illumination (CIE) has also cautioned that the term “blue light hazard” is often used inaccurately when discussing ordinary light exposure and actual eye-damage risk. CIE
Therefore, this experiment should be treated as a light measurement test, not an eye-safety evaluation.
Why Can Smartphone Measurements Change So Much?
A smartphone is not a fixed-output laboratory light source.
Changing the screen brightness can immediately change the measured illuminance and irradiance.
The image displayed on the screen matters too. A bright white screen and a dark interface can produce very different readings.
Viewing distance is another major variable. Moving the sensor closer to or farther away from the screen changes how much light reaches the measurement point.
Display settings such as Night Mode, Eye Comfort Mode or warmer color-temperature settings may also change the spectral distribution.
For meaningful comparisons, change only one variable at a time.
Can You Compare Normal Mode and Night Mode?
Yes.
A useful follow-up experiment would be to keep the same phone, screen content, brightness, viewing distance and sensor position, then compare:
Normal display mode vs. Night / Eye Comfort mode.
Measurements such as Blue Scale, irradiance and CCT can then show how the display output changes.
That type of A/B comparison is more informative than looking at a single reading in isolation.
Related Blue-Light Test
Want to see what happens when a lens is placed between a blue-light source and the sensor? See our Do Blue-Light Glasses Really Block Blue Light? A Simple Meter Test.
About the Meter Shown in the Video
The original 2025 video shows AH-310 in the app interface.
AquaHorti’s current indoor-light measurement product is AH-300, which measures LUX/FC, CCT, blue-light irradiance and blue-light percentage and supports additional lighting-measurement workflows. AquaHorti also explicitly treats blue-light percentage as a comparative measurement rather than a medical diagnosis or health verdict. AquaHorti
Learn more: AH-300 Light Meter – LUX, CCT & Blue-Light Measurement
Frequently Asked Questions
Does a smartphone screen emit blue light?
Yes. Smartphone displays emit visible light containing a blue-light component, which can be measured as part of the screen’s optical output.
How much blue light did the phone produce in this test?
Under the conditions shown in the video, the meter displayed a Blue Scale value of approximately 19.11% and an Irradiance (Ee) of approximately 0.1 W/m².
Does a 19.11% Blue Scale reading mean the phone is harmful?
No. Blue Scale is a measurement parameter and should not be interpreted as a medical safety threshold.
Can a light meter determine whether a phone will damage someone’s eyes?
No. A light meter measures optical characteristics such as illuminance, CCT and blue-light parameters. It does not diagnose eye damage or establish medical safety.
What factors can change a smartphone blue-light measurement?
Screen brightness, displayed content, viewing distance, viewing angle, display mode and ambient lighting can all affect the result.