There are so many eye protection table lamps, which parameters are really important?

"Eye-protecting desk lamps" are the hardest hit area with overflowing marketing concepts - almost every desk lamp claims to be "eye-protecting", but the parameters that really affect eye comfort are not even written on the packaging of many products. This article helps you understand the core indicators of desk lamps.

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Strobe: the most easily overlooked hazard

What is strobe

The brightness of the light source changes periodically with time, which is called flicker. The human eye cannot directly perceive high-frequency strobes, but the brain can receive this signal. Exposure to a strobe environment for a long time can cause visual fatigue, headaches, and decreased concentration.

Two types of strobe

100/120Hz strobe (low frequency):

• Older fluorescent lamps and common electronic ballasts, synchronized to AC frequency (50Hz × 2 = 100Hz)
• Can be perceived by the human eye (flickers can usually be seen directly at frequencies below 100Hz)

Flicker caused by high-frequency PWM dimming:

• PWM (Pulse Width Modulation) is commonly used for dimming LED lights. When it is dark, the light will switch on and off quickly at a high frequency.
• PWM dimming below 500Hz: still affects some people
• The higher the frequency (> 1000Hz), the less impact it has on people

How to judge whether the desk lamp is flickering

Mobile phone camera test method:

1. Turn on the phone camera (camera mode or front camera)
2. Without using flash, point the lens towards the desk lamp
3. If horizontal black stripes scroll on the screen, it means there is flicker.
4. The fewer and slower the stripes, the lower the frequency (the greater the problem); no stripes means extremely high frequency or no stroboscopic

Standard Reference

Chinese National Standard GB/T 9473 Hygiene Standard for Learning Tools (2017 Edition):

• Requires the desk lamp to strobe without visible flicker
• "Flicker-Free": Flicker ratio < 5% (detected above 1000Hz)

Recommended: Purchase desk lamps clearly marked "Flicker Free" or "DC Drive"

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Color temperature: affects learning efficiency and sleep

Color temperature (in K, Kelvin) describes the color of light:

Color temperature	Light color	Subjective feeling	Suitable for the scene
2700–3000K	Warm white	Warm, relaxing	Bedroom, reading and resting
3500–4000K	Neutral white	Comfortable and natural	Living room, multi-functional area
4000–5000K	Cold white	Sober, focused	Study, work, reading
5000–6500K	Cool white/daylight white	Highly awake	Work during the day, not suitable for night

Effects on Eyes:

• High color temperature (6000K+): There are many blue light components, which will inhibit melatonin secretion and affect sleep; it can also cause visual fatigue for a long time
• Recommended light for studying: 4000–5000K (daytime); reading before going to bed: below 3000K

Multiple color temperature adjustment: Some desk lamps support 3 levels or stepless adjustment, which can be switched according to the usage scenario. It is recommended to purchase.

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Illumination (lux): Is it bright enough?

The unit of illumination is lux, which represents the amount of light falling on the work surface.

National standard GB/T 9473 requirements for study lamps:

• Desk lamp center illumination (direct light at 0.35m) ≥ 500 lux
• Illumination uniformity (minimum/average) ≥ 0.7

Why uniformity is important:

• Uneven illumination means there are bright and dark areas on the paper
• Eyes repeatedly switch between light and dark areas, causing fatigue
• Some desk lamps are very bright in the center and very dark at the edges, which makes them uncomfortable to use.

Test method: Download the illumination measurement APP (such as Lux measurement) on your mobile phone, measure it at the normal use position of the desk lamp (about 35cm below the desk lamp), and compare it with the promotional data.

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Color Rendering Index (Ra/CRI)

The color rendering index represents the ability of light to restore the true color of an object, with a perfect score of 100 (equivalent to sunlight).

Ra value	Suitable scene
Ra ≥ 80	Basic daily use (qualified)
Ra ≥ 90	Recommended for study and fine work
Ra ≥ 95	Drawing, printing, color judgment

Problems with low Ra values: Color distortion. Working in a distorted color environment for a long time requires the eyes to work extra hard to identify, leading to fatigue.

Recommendation: Choose a study desk lamp with Ra ≥ 90.

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AA grade table lamp standard

China has an industry standard specially formulated for student desk lamps: AB Standard (QB/T 1034)

Level	Core Requirements
Level AA	Illumination, uniformity, and flicker all reach higher standards
Level A	Basic pass

"Grade AA" marked on the product packaging means it has passed this certification and is more reliable than ordinary desk lamps.

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Table lamp placement position

Correct location:

• Writing with the right hand → Place the desk lamp in front of the left (to prevent the hand from blocking the light and causing shadows)
• Writing with the left hand → Place the desk lamp on the right front
• Desk lamp height: The bottom of the lamp should not be lower than eye level (to prevent glare)

Maintain background ambient light at the same time: The brighter the desk lamp is not, the better. The gap between the brightness of the surrounding environment and the brightness of the desk lamp is too large, and the eyes have to frequently adapt between bright light and darkness, which makes it more tiring. It is recommended that when the desk lamp is on, the main light in the room should also maintain a certain brightness.

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*This article refers to GB/T 9473-2017 "Performance Requirements for Reading and Writing Desk Lamps" and QB/T 1034 Student Eye Protection Desk Lamp Standard. *