Mechanism one: the test method is not standardised across the category
Spec inflation is usually described as a lie, and sometimes it is. More often it is the result of a fragmented industry where the same words are used for different measurements and where the person writing the spec sheet is not the person who ran the test. A buyer who understands the mechanism is better placed to ask for the thing that was actually measured. This article is about the mechanisms. Photometric measurement depends on the machine, the mode, the distance, the drive current, the ambient temperature and the warm-up. Within one factory these may be consistent; across factories they are not. Two lanterns can report the same figure for different reasons, and two lanterns can report different figures for the same physical output.
The mechanism is not deception. It is that the figure is a property of the measurement rather than of the product, and the measurement differs. The result is that a comparison table built on headline figures is a comparison of measurement practices as much as of products.
The counter is a request for the conditions, which is what lumens without test conditions sets out in the eight-row table.
Mechanism two: brightness and capacity are measured in different units
Runtime and output are related but they are not the same quantity. A lantern that is driven harder produces more light and consumes more power, so the runtime at a higher brightness falls faster than the light output rises. A spec sheet that presents one runtime figure and one lumen figure has presented two settings as though they were one product.
The mechanism here is the mixing of definitions. A combined lumen figure may be a sum over modes, and the runtime figure may belong to the lowest mode, so the two numbers describe different operating points. Neither is wrong. Read together they are incoherent.
The counter is to ask for runtime at each brightness level with the capacity, starting voltage, ambient temperature and cutoff stated, which is the split described in runtime per brightness level.
Mechanism three: weather and durability claims are made from a single test
Weather performance is multi-dimensional. External water, dust, thermal cycling, condensation and corrosion are different phenomena with different tests. A single result is often presented as though it covered the others.
The mechanism is the attractiveness of one number. One number is easy to print, easy to compare and easy to defend in a short conversation. Several numbers with conditions are harder to print and harder to compare, so they are less likely to appear.
The counter is to ask what was tested, for how long and under what conditions, and to ask specifically whether the claim covers internal condensation, which it usually does not. IP-rated ingress claims and the condensation gap sets out that boundary.
Mechanism four: the commercial pressure to be the largest number in the column
Comparison tables reward the largest figure. A buyer scanning ten rows will read the highest lumens, the longest runtime and the most generous ingress claim without reading the conditions, because the conditions are usually in a separate document.
The mechanism is therefore commercial rather than technical. A supplier who quotes honest conditions can lose a shortlist to a supplier who quotes a favourable method. This is why the counter is not only to ask for conditions but to ask for them at the quotation stage, before the comparison is made.
Mechanism and counter
| Mechanism | What it produces | The counter to request |
|---|---|---|
| Uneven test methods | Same figure, different measurement | Machine, mode, distance, current, ambient, warm-up |
| Mixed definitions | Two numbers from different operating points | Runtime and output split by brightness level |
| Single-test weather claims | One number covering several phenomena | The specific procedure, duration and conditions |
| Largest-number competition | Conditions omitted from the comparison table | The condition sheet attached to the quotation |
| Sample identity drift | A figure for a sample the buyer has not seen | Golden sample, pre-production or batch identity |
Mechanism five: sample identity drifts
A figure measured on a golden sample is a figure for that sample. A figure measured on a pre-production unit may differ from the production batch, and a figure measured on a batch may not represent a later batch. The mechanism is that the measurement is real but the subject has changed.
The counter is to ask what the sample was, when it was made and whether the test conditions apply to the shipped product. A test on a hand-built unit is not a test on the production tooling.
A spec sheet ≠ a test report
A spec sheet is not a test report. It is a summary written for a buyer, and it may describe the sample rather than the batch. The buyer should treat the sheet as a claim to be verified rather than as evidence.
A second boundary: a consistent factory is not a validated factory. Consistency across its own products does not establish that its method matches another factory's method, so cross-factory comparison still needs the conditions.
A third boundary: a buyer asking for conditions is not being hostile. Most factories run the tests and keep the records; the difficulty is usually in the presentation rather than in the measurement.
Five questions for the supplier
- Which test method produced the headline figure, and what were the machine, mode, distance, drive current, ambient temperature and warm-up? These define the measurement.
- Which brightness mode does each runtime figure belong to, and is the capacity stated in nominal or usable terms? Mixed definitions make the numbers incoherent.
- Which weather tests were run, for how long and under what conditions, and do they cover internal condensation? One number rarely covers several phenomena.
- What was the sample: golden sample, pre-production or production batch, and when was it made? The figure should describe what ships.
- Will you attach the condition sheet to the quotation rather than after the order, and repeat it at sample approval? The comparison should be made on the conditions.
Next step
Attach the five questions to the request and ask the supplier to answer in writing at quotation stage. Then compare on the conditions rather than on the headline column. Related reading: lumen inflation and IP stacking for the site's position on the practice, lumens without test conditions for the condition table, and quote comparison beyond the unit price for how to build the comparison. To hold a quotation to these conditions, start at contact.
Part of the Lumizuno outdoor-lighting notes. Illustrative values only; lumens and ingress ratings must be read with their test conditions.