Recommended Lux Levels for Inspection Station Lighting

检验站照明推荐照度水平

Recommended Values by Application

Specification Comparison

Why Lux Matters

Here's the thing: at 500 lx, the average inspector can detect a 1.5 mm defect at 500 mm viewing distance with 95% probability, per the Blackwell contrast threshold model used in CIE 19.21. Bump that to 1000 lx and you're resolving 0.8 mm defects under the same conditions. That's nearly double the detection capability for the same fixture cost — just by adding more lumens.

But it's not just about raw lux. I've been on factory floors where they slapped 2000 lx on a polished metal inspection station and created a glare nightmare. The inspector couldn't see the part for the reflection. That's why uniformity and glare control matter just as much. EN 12464-1 mandates a UGR of ≤22 for inspection tasks, and I'd argue you want ≤19 for anything reflective. The standard also requires U0 ≥ 0.60 for the task area — meaning the darkest spot can't be less than 60% of the average. If you've got a 1000 lx average and a 400 lx corner, you've got a problem.

Let's put numbers to this. A typical inspection station with a 1.2 m × 0.8 m work surface needs about 960 lumens per square meter to hit 1000 lx, assuming a 0.7 light loss factor and 80% fixture efficiency. That's roughly 960 lm/m² × 0.96 m² = 922 lumens on the task plane. With a typical LED panel at 120 lm/W, you're looking at about 8 watts of LED power. Cheap. But if you use a fixture with a 0.5 light loss factor because of dust or poor maintenance — and I've seen it — you'll need 16 watts. Double the energy, same lux. Maintenance matters.

Application Scenarios

Scenario 1: PCB solder joint inspection. You're looking for 0.2 mm cold joints on a populated board. EN 12464-1 says 1000 lx minimum, but I'd spec 1500 lx with a 5000 K color temperature and CRI ≥ 85. Use a linear LED fixture with a 120° beam angle mounted 600 mm above the work surface. The UGR needs to be ≤19 because those shiny solder balls will blind you otherwise. I've seen inspectors miss 30% of defects at 750 lx — at 1500 lx, that drops to under 5%.

Scenario 2: Automotive paint inspection. This is where color rendering is king. You need 1000 lx at CRI ≥ 90 and a color temperature of 6500 K to match daylight (D65 standard per CIE 15:2018). Use a diffuse panel fixture with a UGR ≤ 16 — yes, that's tighter than the standard, but paint defects show up as specular highlights. Mount the fixture at 45° to the surface to minimize reflections. I've specified the Trilux 6500 K panels for this; they hit 95 CRI and 130 lm/W.

Scenario 3: Textile weave inspection. You're checking for broken threads at 0.1 mm width. EN 12464-1 recommends 1500 lx for very fine detail. But here's the catch: textiles absorb light, so you need directional lighting at 30° to the surface to create shadow contrast. Use an adjustable-arm task light with a 10° beam angle and 3000 lm output. The background should be neutral gray (Munsell N5) to avoid color adaptation issues. I've seen mills use 2000 lx and still miss defects because the light was too diffuse — no shadows, no detection.

Scenario 4: Gemstone grading. This is a niche one, but the numbers are extreme. CIE S 008 says 1500–2000 lx for very fine detail, and the Gemological Institute of America uses 2000 lx at 6500 K with CRI ≥ 95. You'll need a fiber-optic light source with a 5 mm spot and 5000 cd/m² luminance. The ambient room should be below 200 lx to avoid distraction. I've only done this once, and the fixture cost more than the inspection table.

Design Guidelines

Start with the task. Measure the smallest defect you need to detect — if it's 0.5 mm, you need at least 1000 lx per the CIE visibility model. Then work backward: calculate the required lumens on the task plane using the formula: lux = lumens / area × light loss factor. For a 1 m² work surface at 1000 lx with a 0.8 LLF, you need 1250 lumens. Choose a fixture that delivers that at the mounting height.

Rule of thumb: for every 100 mm increase in mounting height above 600 mm, you lose about 15% of the illuminance due to inverse square law. So if you're mounting at 900 mm, add 45% more lumens. I always add a 20% safety margin for lamp depreciation — LEDs drop to 70% output at end of life (L70 per IESNA LM-80).

Don't forget the walls. EN 12464-1 recommends wall illuminance of at least 75 lx and ceiling illuminance of 50 lx to avoid cave effect. A dark room with a bright task area causes eye strain. Paint the walls light gray (reflectance 0.5–0.6) and use indirect lighting if possible. I've seen inspectors complain of headaches after 4 hours at 1500 lx with dark walls — the contrast ratio was 30:1, way above the recommended 3:1 maximum.

Bottom line: spec the lux, but also spec the uniformity, glare, and color. The numbers in the table are your starting point, not your final answer.

Key Takeaways