Comparative Study on Optical Performance of Mainstream Lighting Fixtures Based on LISUN Digital Lux Meter

Abstract​:Aiming at the unclear difference in optical performance among five types of mainstream lighting fixtures in the market, namely bulb lights, PAR lights, LED lights, street lights and tubes, this study adopted the LISUN LMS-6000 Digital Lux Meter (full-function version LMS-6000SF) to conduct a systematic test on key optical parameters of the five types of fixtures, including illuminance, correlated color temperature (CCT), color rendering index (Ra), peak wavelength, flicker depth and retinal blue light hazard. Through scientific design of the test scheme, accurate data collection and comparative analysis, the performance advantages and applicable scenarios of various types of fixtures were clarified. The results show that street lights have outstanding performance in illuminance and anti-flicker, PAR lights have the best color rendering index, and LED lights have balanced comprehensive performance. This study provides reliable data support and technical reference for lighting engineering selection, product quality control and improvement of industry standards.

1. Introduction​
With the continuous innovation of lighting technology, bulb lights, PAR lights, LED lights, street lights and tubes have been widely used in home, commercial, outdoor and other fields. The optical performance of these lighting fixtures is directly related to lighting quality, visual health and energy consumption, so accurate performance evaluation is of great practical significance.​
Traditional lighting fixture testing methods often require the cooperation of multiple professional equipment, with complex operation procedures, and are limited to laboratory environments, which are difficult to meet the needs of on-site rapid testing. The LISUN LMS-6000 series Digital Lux Meter effectively solves this problem with its advanced technical advantages. This instrument adopts a telephoto cross-asymmetric CT spectroscopic system, which can realize synchronous testing of multiple parameters such as illuminance, color temperature, color rendering index, flicker and blue light hazard. The wavelength accuracy reaches ±0.5nm, and the illuminance test range covers 0.1-500000lx. At the same time, it has a 4000mAh lithium battery for long battery life (continuous operation for 20 hours) and 8GB data storage (capable of storing 100,000 reports). It can easily cope with long-term and multi-scenario on-site testing work, providing an ideal testing tool for this multi-category lighting fixture comparison study.​

LMS-6000 Portable CCD Spectroradiometer

2. Design of Test Scheme​
2.1 Test Instrument​
In this study, the LISUN LMS-6000SF full-function Digital Lux Meter was selected, and its core technical parameters are as follows:​
• Wavelength range: 350-950nm, which can fully cover the visible light, near-infrared and ultraviolet bands, meeting the spectral testing needs of various lighting fixtures;​
• Test accuracy: chromaticity coordinate accuracy ±0.005, color temperature accuracy ±0.6%, color rendering index accuracy ±(0.3% rd±0.3), ensuring the accuracy and reliability of test data;​
• Functional characteristics: supporting flicker test (modulation depth 0-100%), retinal blue light hazard assessment (in line with GB/T20145 and CIE S009/E:2002 standards) and plant lighting parameter test, with comprehensive functions and suitable for practical application scenarios;​
• Software compatibility: the supporting PC software is compatible with Win7-Win11 systems, facilitating data export, analysis and report generation, and improving the efficiency of testing work.​

2.2 Test Samples​
To ensure the representativeness and objectivity of the test results, 3 samples of each of the five types of lighting fixtures were randomly selected from the market, and all samples meet the mainstream industry specifications and standards. The specific information is as follows:​
• Bulb light: power 10W, color temperature marked “warm white 3000K”, mainly used for home indoor lighting;​
• PAR light: power 20W, color temperature marked “neutral white 4500K”, often used in commercial windows, exhibition halls and other scenarios that need to highlight the color of objects;​
• LED light: power 15W, color temperature marked “cool white 6500K”, a general-purpose indoor lighting fixture;​
• Street light: power 60W, color temperature marked “cool white 5000K”, specially designed for outdoor road lighting;​
• Tube: power 18W, color temperature marked “warm white 3500K”, widely used in strip lighting in offices, classrooms and other places.​

2.3 Test Environment and Process​
• Environment Control: A professional darkroom test environment was built, and the ambient temperature was stably controlled at 25℃ to avoid interference from external stray light on the test results. Referring to GB/T 9473-2017 “Performance Requirements for Desk Lamps for Reading and Writing”, the test distance was uniformly set to 1m to ensure the consistency of test conditions;​
• Instrument Calibration: Before the formal test, the built-in standard light source of the LISUN LMS-6000SF was used to calibrate the instrument, ensuring that the test accuracy of key parameters such as wavelength and illuminance meets the experimental requirements;​
• Data Collection: Each lighting fixture sample was tested continuously for 3 times, and parameters such as illuminance, correlated color temperature (CCT), color rendering index (Ra), peak wavelength, flicker depth and blue light hazard weighted irradiance were recorded respectively. The average value of the 3 test results was taken as the final test data of the sample;​
• Data Verification: The original spectrogram was exported through the PC software supporting the instrument to verify the consistency and rationality of the test data, eliminate abnormal data, and ensure the validity of the experimental data.​

3. Test Results and Analysis​
3.1 Test Results of Core Optical Parameters​
The test results of core optical parameters of the five types of lighting fixtures are shown in the following table. The data in the table are the average values of 3 tests for each sample, which can objectively reflect the optical performance level of various types of lighting fixtures.

3.2 Detailed Analysis of Each Parameter​
3.2.1 Illuminance and Color Temperature​
• Illuminance Performance: From the test data, the average illuminance of street lights is the highest, reaching 2596.7lx, which is consistent with the design goal of street lights to provide sufficient lighting for outdoor roads and can effectively ensure the safety of driving and pedestrians at night; the average illuminance of PAR lights is 1263.9lx, which is at a medium to high level, and can meet the needs of local high-intensity lighting in commercial scenarios, such as highlighting the products in the window; the illuminance of bulb lights (893.5lx) and LED lights (1025.3lx) is moderate, suitable for basic lighting in indoor places such as homes and offices; the average illuminance of tubes is the lowest, 785.5lx, which is more suitable for lighting in narrow spaces with low requirements for light intensity.​

• Color Temperature Consistency: The deviation between the actual test color temperature and the marked color temperature of the five types of fixtures is small, all within 3%, which meets the relevant error standards in GB 7000.1-2015 “Luminaires – Part 1: General Requirements and Tests”. Among them, PAR lights (deviation 0.18%) and street lights (deviation 0.34%) have the best color temperature consistency, reflecting the advantage of industrial lighting products in color temperature control accuracy; the color temperature deviation of bulb lights (deviation 0.4%), LED lights (deviation 0.2%) and tubes (deviation 0.25%) is also within a reasonable range, which can meet the demand for color temperature stability in daily lighting.​

3.2.2 Color Rendering Index and Peak Wavelength​
• Color Rendering Index: The color rendering index (Ra) is an important indicator to measure the ability of a luminaire to restore the true color of an object. The higher the Ra value, the better the color rendering performance. The test results show that the average color rendering index of PAR lights is the highest, reaching 92.5, which is a high color rendering luminaire and can accurately restore the original color of objects. Therefore, it is particularly suitable for scenarios with high requirements for color restoration, such as museums, art galleries and high-end commercial windows; the average color rendering index of tubes is 83.6, and that of LED lights is 85.5, both of which have good color rendering performance and can meet the needs of most daily lighting scenarios such as homes and offices; the average color rendering index of bulb lights is 81.4, which can basically meet the requirements for color restoration in ordinary home lighting; the average color rendering index of street lights is the lowest, 78.5, because the design focus of street lights is to provide high-brightness lighting to ensure traffic safety, rather than pursuing extreme color restoration, and its color rendering performance is still within an acceptable range.​

• Peak Wavelength: The peak wavelength reflects the concentrated area of the spectral energy distribution of the luminaire. The peak wavelength of LED lights is concentrated at 450.5nm, which is in the blue light band, which is consistent with the spectral characteristics of cool white LED lights; the peak wavelength of bulb lights, PAR lights, street lights and tubes is in the yellow-green light band of 540-560nm. The light in this band is more in line with the human eye’s demand for visual comfort, so these luminaires give a softer visual feeling when lighting.​

3.2.3 Flicker and Blue Light Hazard​
• Flicker Depth: Flicker refers to the phenomenon that the light output of a luminaire changes periodically with time. Excessively high flicker depth will cause visual fatigue of the human eye, and long-term exposure may also affect visual health. According to the “LED Lighting Product Flicker Test Method”, a flicker depth of ≤3% is a non-hazardous level. The test data shows that the average flicker depth of street lights is the lowest, only 0.7%, which is far below the safety threshold, and can effectively avoid visual fatigue caused by long-term outdoor lighting; the average flicker depth of PAR lights is 1.8%, and that of LED lights is 2.4%, both within the safe range, so they are relatively safe to use; the average flicker depth of bulb lights is 3.1%, which is close to the safety threshold, and sensitive people may feel slightly uncomfortable when using it for a long time; the average flicker depth of tubes is the highest, 4.0%, which does not cause serious harm to the human body, but long-term work or study under such luminaires will increase the risk of visual fatigue.​

• Blue Light Hazard: Blue light hazard mainly refers to the potential damage to the human eye retina caused by blue light with a wavelength of 400-500nm. According to the CIE S009/E:2002 standard, the blue light hazard weighted irradiance of ≤200μW/cm² is the safe range. The blue light hazard weighted irradiance of the five types of fixtures is far below the safety upper limit, among which bulb lights have the lowest (12.7μW/cm²) and LED lights have the highest (23.6μW/cm²). Although the blue light hazard of LED lights is relatively high, it is still within the safe range, so there is no need to worry too much about daily normal use; street lights and bulb lights have low blue light hazard, and are more suitable for long-term use by sensitive groups such as children and the elderly.​

4. Conclusions and Recommendations​
4.1 Conclusions​
Obvious Performance Differences: Due to different application scenarios and design goals, the five types of lighting fixtures show significant differences in optical performance. The core advantages of street lights lie in high illuminance and low flicker, which can meet the safety needs of outdoor road lighting; PAR lights are characterized by high color rendering index, and are ideal choices for scenarios with high requirements for color restoration; LED lights have balanced performance in terms of illuminance, color temperature, color rendering index and flicker, and low energy consumption, making them general-purpose lighting products with excellent comprehensive performance; bulb lights and tubes focus more on meeting the basic indoor lighting needs, and are more suitable for home, office and other scenarios in terms of illuminance and color temperature.​
Outstanding Instrument Advantages: The LISUN LMS-6000SF Digital Lux Meter showed strong performance advantages in this test. It can not only realize synchronous and accurate testing of multiple parameters, but also has good portability and battery life, and can easily cope with on-site testing work. Its test data is accurate and reliable, providing strong technical support for the comparative analysis of luminaire performance, and it is an efficient tool for lighting product quality testing and performance research.​

4.2 Recommendations​
• Scenario-Based Selection: In actual lighting engineering and consumer purchase, appropriate fixtures should be selected according to specific scenario needs. For home lighting, bulb lights (low blue light, comfortable color temperature) should be given priority; for commercial windows and exhibition halls, PAR lights (high color rendering) are recommended; for outdoor road lighting, street lights that meet the standards (high illuminance, low flicker) must be selected; for offices, LED lights or tubes can be reasonably selected according to the demand for light intensity.
• Quality Control: Lighting fixture manufacturers can adopt the LMS-6000 series Digital Lux Meter to establish an ex-factory inspection system, focusing on monitoring parameters such as color temperature, color rendering index and flicker, so as to prevent unqualified products from entering the market.
• Follow-up Research: The scope of samples can be expanded by adding comparative tests of lamps with different powers and brands, so as to further improve the performance database of lighting products and provide data support for the optimization of industry standards.