Goniophotometer Testing: How to Read a DXZ Illuminance Report

A GO-HD report shows you one thing: an illuminance pattern under a stated test setup. Before you compare two reports, line up the basics. That means the mounting height, the measurement area, the electrical condition, the lamp configuration and the aiming.

That map describes the tested area, and nothing beyond it. It won’t tell you how far a driver actually sees. It can’t predict a different installation. And it isn’t one brightness number: instead of a single headline lumen figure, the scan maps intensity across a grid of angles.

We run the instrument ourselves, in-house. This page explains what it measures, what our own GO-HD reports actually record, and where the method’s limits are.

Dataset

100 GO-HD reports

Equipment

EVERFINE GO-HD

Measurement

H = 1.000 m · 5° step

Source

DXZ in-house archive

What Is a Goniophotometer?

That distinction matters.

A lumen number tells you how much light leaves the fixture. A goniophotometer tells you where it lands — and for a driving light or a work light, “where it lands” is the whole product.

Goniophotometer Types: Why Coordinates Differ

Goniophotometers differ in one main way: how the lamp and the detector are oriented while the scan runs. Three standard geometries cover most of the work:

What this means for a buyer: the geometry has to match the product, but the letters alone don’t settle suitability. Labs differ in their coordinate systems and test setups. What matters is the mounting orientation, the angular range covered, the surveyed area and the purpose of the scan. Our own GO-HD reports use a road-facing, forward-looking setup, because that is how our products are used.

Inside Our Lab: Our EVERFINE GO-HD Setup

We produce our road-facing photometric measurements on an EVERFINE GO-HD system. A defined horizontal and vertical measurement window generates the equal-illuminance distributions, and the electrical test data is logged alongside.

Every report records the same conditions. Here they are, exactly as printed on the report:

Three things we want to be clear about:

1. H = 1.000 m is fixed for every report in the archive. One shared height controls one variable — it doesn’t make two reports comparable on its own. Check the rest first: measurement area, aiming, lamp configuration and drive voltage.
2. The measurement window is deliberately narrow. We use it to capture a road-facing beam pattern, not to sweep a full sphere. So it isn’t an IES or LM-79 distribution test, and we don’t present it as one.
3. Every report carries its electrical context — voltage, current, power, power factor. Optical output without the drive conditions can’t be reproduced. In practice this matters: 99 of the 100 reports are logged at ≈ 13.2 V, and one report (8C01) is a 24 V system. We flag that one separately instead of mixing it into a 13.2 V ranking.

How a Photometric Test Runs

Each test runs through four stages, all in-house. Nothing is subcontracted.

1. Sample mounting and test-condition setup. The lamp goes into the test position, and the test conditions are recorded before the scan starts.
2. Angular scan. The GO-HD steps the sample through the fixed angular grid, and the detector records intensity at each position.
3. Data capture and electrical logging. Illuminance values are captured with the live electrical parameters (≈ 13.2 V, current, power, power factor 1.000). This is what ties an optical figure back to a drive condition.
4. Report issued and archived. The output — peak illuminance plus an equal-illuminance map with contour lines — gets signed by the operator and kept in the DXZ archive.

That last point is worth repeating: we keep the reports.

Test reports and certification records answer different questions. A certificate confirms that a declared product conforms to a standard. A test report records what one sample measured under a stated setup. This page is about the second kind only, which is why the conditions are printed alongside every figure.

What 100 In-House Reports Show

This is the point of a first-party archive: the products, the instrument and the reports all come from us.

Across 100 unique GO-HD illuminance reports — 95 distinct model identifiers — all at a uniform H = 1.000 m:

• Peak illuminance ranges from 18.18 lx to 652.0 lx, with a median of 108.75 lx.
• The distribution leans heavily toward the low end — exactly what you would expect from a portfolio that includes compact marker and interior units alongside high-output bars.
• A few models were re-scanned at a different measurement-area setting, so the archive holds slightly more reports than model identifiers. We count per report — we don’t quietly average the two.

Here is the top of that distribution. Every value comes straight from the source reports.

Source format for every row: 照度测试/<file>.pdf ｜ GO-HD ｜ <date>.

* Peak illuminance per watt is a derived directional-performance ratio under this test geometry. It is not luminous efficacy (lm/W) — efficacy is a total-output figure and it comes from the integrating sphere, not from this measurement. Nor is it a universal optical-quality score. The ratio depends on the surveyed area, the mount height and the aiming. Compare it only between reports recorded under the same geometry.

One report sits outside the 13.2 V series, and we keep it out of the table above on purpose. 8C01 is the only 24 V unit in the archive. It recorded 652.0 lx at 155.35 W (report 2026-04-24). That is a real figure, taken on the same instrument at the same mount height, but at a different supply condition. So we show it here as a condition-bound reading, not as part of a 13.2 V sort.

Comparing like with like (13.2 V only): under the same test setup, 10C03 produced 477.1 lx at 58.89 W, while 9R04 produced 515.4 lx at 106.03 W. That is about 92.6 % of the peak illuminance from 55.5 % of the power. The point: beam concentration and total luminous output are two different design variables, and the goniophotometer tells them apart.

Download a real photometric report

See the full report, not just the summary. We’ve prepared two of our actual GO-HD illuminance reports — PY35-1-Flood (white) and BF4-9 — as sample downloads, with vendor-sensitive fields redacted. Same instrument, same conditions, same contour format you’d get on a real project.

Or request data for your model

Photometric data is available on request. Our GO-HD example is a partial road-plane illuminance report. If you need an IES-compatible photometric file (LM-63 format) for a specific model and application, ask us. We’ll confirm whether the angular dataset you need exists, and what it covers. Tell us which product you’re specifying and we’ll confirm scope and turnaround.

How to Read an Equal-Illuminance Map

Peak lux is only half the story. The contour lines on the report show how the measured illuminance is spread across the road plane.

Two samples from our archive, with the measurement area exactly as each report records it:

• PY35-1-Flood (white) — peak 175.3 lx, reported measurement area L = 220.0 m × W = 50.0 m (2026-06-11).
• BF4-9 — peak 230.6 lx, reported measurement area L = 520.0 m × W = 40.0 m (2026-05-27).

The 1 lx contour shows how far the measured illuminance field reaches under the stated test geometry. It should not be read as a direct vehicle visibility distance. Real seeing distance also depends on target reflectance, ambient light, mounting height, aim, road conditions and glare.

That is why we publish the contour, not just the headline peak value. It shows the shape and reach of the measured field — and nothing more.

Goniophotometer vs Integrating Sphere: Which Test Do You Need?

These two instruments answer different questions, and a complete photometric file needs both.

We run both. Ask for the goniophotometer data if your question is beam coverage. Ask for the sphere if it is total output or color consistency across a production batch. And if you want the units themselves untangled first — lumens vs candela vs lux — read that article before either report.

FAQ