GB-standard illuminance testing determines whether reading and writing desk lamps meet the Grade A and Grade AA brightness requirements of GB/T 9473, China's national performance standard for eye-protection lamps. This article explains the scope of testing, the measurement grid and pass criteria, the instrumentation used by accredited third-party laboratories, and how manufacturers, brands, and retailers use the resulting test reports for product development and market claims.
Technical Overview
Illuminance, expressed in lux (lx), is the luminous flux incident on a unit area of the working surface and is the single most important quantitative indicator of whether a desk lamp delivers adequate, comfortable light for reading and writing. In China, eye-protection lamps are evaluated against GB/T 9473, "Performance requirements for reading and writing desk lamps," the current edition of which supersedes the earlier 2017 version. The standard classifies lamps into Grade A and Grade AA based on the illuminance achieved over a defined working zone of the desk surface, and it further addresses illuminance uniformity, glare, shading, correlated color temperature, color rendering, retinal blue light hazard, and flicker.
Illuminance testing under GB/T 9473 is typically performed alongside a family of complementary standards, including:
- GB/T 9473 for photometric performance and illuminance grading of reading and writing desk lamps
- GB 7000.1, aligned with IEC 60598-1, for luminaire safety requirements
- GB/T 20145, aligned with IEC 62471, for photobiological safety and blue light hazard classification
- IEEE 1789 and IEC TR 63158 as references for flicker and stroboscopic effect evaluation
- ISO/IEC 17025 as the general competence requirement for laboratories performing the tests
Together, these standards form the technical basis on which "national standard Grade AA" claims for eye-care lamps are substantiated by accredited third-party laboratories.
Testing Samples
Mains-Powered LED Desk Lamps
Plug-in alternating-current desk lamps represent the largest product category submitted for illuminance grading. Samples are tested at their rated supply voltage and frequency, in the normal working attitude declared by the manufacturer, with any adjustable arm or lamp head set according to the installation instructions.
Rechargeable, USB-Powered, and Battery Models
Portable lamps that operate from an internal battery or a USB supply are evaluated in each declared power mode. Battery-powered operation is tested with a fully charged battery at the beginning of each measurement sequence, and dimming levels relevant to any eye-protection claim are assessed separately.
Clip-On and Clamp-Mounted Reading Lamps
Clamp-type luminaires are fixed to a reference board edge of the thickness range specified by the standard, and the measurement grid is established relative to the projection of the light-output center onto the desk plane, exactly as for freestanding models.
Floor-Standing and Architectural Reading Lights
Floor lamps and wall-adjacent fixtures marketed specifically for reading and writing tasks may also be assessed, with the measurement plane positioned at the desk height or seated-reading height declared by the manufacturer.
Testing Items
A complete GB/T 9473 evaluation covers the photometric parameters that determine illuminance grading as well as the optical characteristics that support an eye-protection designation. Core items include:
- Central-zone and outer-zone illuminance for Grade A or Grade AA determination
- Illuminance uniformity across the defined working area
- Glare control and shading performance, including light distribution above the horizontal plane
- Correlated color temperature (CCT) and general color rendering index (Ra), with supplementary evaluation of the R9 saturated-red rendering value
- Retinal blue light hazard classification, with the exempt group (RG0) expected for lamps intended for children
- Temporal light artifacts, including percent flicker, flicker index, and stroboscopic visibility measure (SVM)
- Luminous flux, luminous efficacy, input power, and power factor as supporting electrical and photometric data
The illuminance grade achieved in testing is the parameter most frequently cited in product marketing and is the headline result of the test report.
Testing Methods
Test Environment and Instrumentation
Measurements are performed in a photometric darkroom in which stray and ambient illuminance is maintained at a negligible level, typically below one percent of the lowest reading of interest. Ambient temperature is controlled, commonly at 25 ± 2 degrees Celsius. Illuminance is measured with a cosine-corrected illuminance meter verified under metrological regulation JJG 211 to class-A accuracy or better, and calibrated with traceability to national standards. Spectroradiometric instruments used for color temperature, color rendering, and blue light assessment are similarly calibrated. Lamps are energized at rated voltage and allowed to stabilize, usually for at least thirty minutes, until successive readings vary by less than one percent over five minutes.
Sample Positioning and Preparation
The origin of the measurement grid is the projection of the center of the light-emitting area onto the horizontal desk or test-bench surface. The lamp is placed in its declared normal working position; where the head height or angle is adjustable, the configuration specified in the standard's most unfavorable case is applied so that the reported grade is representative of real use. The forward axis of the grid extends away from the lamp, and the transverse axis runs left and right through the origin.
Measurement Grid and Grading Criteria
Illuminance is recorded at a matrix of points covering the central and outer zones of the working surface, and every point within a given zone must satisfy the applicable threshold. The classification criteria are summarized as follows:
- Grade A: illuminance of at least 300 lx throughout the central zone extending approximately 300 mm to the left, right, and forward of the origin, and at least 150 lx throughout the outer zone extending approximately 500 mm left and right and 400 mm forward
- Grade AA: illuminance of at least 500 lx throughout the central zone and at least 250 lx throughout the outer zone, using the same zone geometry
The current edition of the standard additionally introduces illuminance uniformity requirements within the measured zones, expressed as the ratio of minimum to average illuminance, together with refined shading and glare provisions. A lamp is assigned the highest grade for which all points, uniformity, and related requirements are satisfied simultaneously.
Supplementary Optical Measurements
Flicker is characterized by recording the illuminance waveform with a fast photometer and calculating percent flicker and flicker index, with reference to the low-risk guidance of IEEE 1789 and the stroboscopic visibility measure described in IEC TR 63158. Blue light hazard is evaluated spectroradiometrically in accordance with GB/T 20145, and color temperature and rendering indices are measured with a calibrated spectrometer under the same stabilized operating conditions used for the illuminance scan.
Applications
Illuminance test reports issued under GB/T 9473 by accredited third-party laboratories serve a wide range of commercial and technical purposes across the lighting supply chain:
- Product development and quality control, allowing engineering teams to verify optical designs against grade thresholds before mass production
- Substantiation of marketing claims such as "national standard Grade AA" and "eye-protection lamp" on packaging and in advertising
- Document review by e-commerce platforms, which commonly require current test reports for eye-care lighting listings
- School, library, and institutional procurement, where tenders specify a minimum illuminance grade for student desk lamps
- Benchmarking and comparison studies that rank competing products on measured illuminance, uniformity, flicker, and blue light performance
- Regulatory and consumer-affairs investigations verifying that declared performance matches laboratory evidence
Because the standard defines objective, reproducible measurement conditions, its results provide a common technical language between manufacturers, retailers, regulators, and end users.
FAQ
What is the difference between Grade A and Grade AA?
Both grades are defined over the same desk area. Grade A requires at least 300 lx in the central zone and 150 lx in the outer zone, while Grade AA requires at least 500 lx and 250 lx in the corresponding zones, plus compliance with uniformity and related requirements. Grade AA therefore indicates substantially higher and more even illumination for demanding or prolonged reading and writing tasks.
Is illuminance testing under GB/T 9473 mandatory?
GB/T 9473 is a recommended national performance standard rather than a compulsory one, and illuminance grading is voluntary. However, luminaire safety requirements in the GB 7000 series remain mandatory for market access, and any lamp advertised with an illuminance grade or eye-protection claim is expected by platforms, buyers, and regulators to be supported by a valid test report from an accredited third-party laboratory.
How is the measurement origin determined when the lamp head is adjustable?
The origin is always the projection of the center of the light-emitting area onto the working plane in the tested configuration. For adjustable luminaires, the standard prescribes the operating attitude to be used, generally the least favorable position defined by the product instructions, so that the reported grade is conservative and repeatable.
Are different dimming levels and color modes tested separately?
Yes. Lamps offering multiple brightness or color temperature settings are evaluated in each operating mode for which a performance claim is made, because illuminance, flicker, and color parameters can vary significantly between modes.
What should a compliant illuminance test report contain?
A complete report identifies the sample and standard edition, describes the test environment and instrumentation with calibration status, records the measurement grid and point-by-point illuminance data, states the achieved grade, and summarizes the supporting optical results such as uniformity, color rendering, blue light hazard classification, and flicker. Reports from laboratories accredited to ISO/IEC 17025 carry the greatest acceptance for commercial and regulatory use.