About

About Elk Lotus LED

We manufacture LED lighting and write the control software that drives it. This site is the reference material we use internally when specifying, sourcing and inspecting product, published because the same questions come back from customers every quarter.

Who publishes this

Elk Lotus LED is a lighting brand of Long-Term New Media Limited, a company registered in Hong Kong. Our product work covers LED luminaires and light engines together with the mobile applications and controllers that operate them — which means we sit on both sides of a problem that is usually split between two suppliers: the photometric and thermal behaviour of the hardware, and the control protocol that has to survive a customer's Wi-Fi.

That is the perspective these notes are written from. They are not a neutral academic survey. They are what a manufacturer has learned from qualifying components, arguing with suppliers about datasheets, and handling the returns when a specification was met on paper and failed in a building.

What this site covers

Commercial and engineering lighting: the specification, retrofit and acceptance stages of a project rather than the consumer buying decision. The five sections are metrics and standards, selection and calculation, retrofit economics, acceptance and QC, and a set of browser-based calculators.

We deliberately do not cover residential decorating advice, product reviews of other manufacturers' fittings, or news. Those are well served elsewhere and we have nothing to add to them.

How these notes are written

Three rules, and they are the reason this site is smaller than it could be.

1. Standards are cited, never reproduced

Where a requirement comes from EN 12464-1, GB 50034, IEC 62717, CIE 97 or an IES document, we name the document and explain what it governs and how it is commonly misread. We do not copy its tables. Those tables are licensed content belonging to the standards bodies, they are revised — EN 12464-1 changed materially in 2021 — and a number transcribed onto a web page is a number that nobody updates afterwards. If you need the governing value, buy the current edition of the standard that applies in your jurisdiction.

2. Measured data is labelled as measured, or it is absent

Some of what we want to publish requires bench work: no-load power draw across a set of drivers, inrush behaviour, colour consistency within a production batch, teardown comparisons of components at different price points. Those pages are written method-first. The procedure, the instrument, the test conditions and an empty results table go up; the numbers go in when the measurements have actually been taken, and the page is marked data pending in its section index until then.

We would rather publish an empty table than a plausible one. A fabricated measurement in a specification document is not a stylistic problem — somebody selects equipment with it.

3. Worked examples state their inputs

Every calculation on this site shows its formula and its assumptions, and the calculators run entirely in your browser so you can change the inputs and see what moves. Where an example uses a manufacturer's published figure, the manufacturer and the document are named.

What we are not

Not a design practice. Lighting design for an occupied building involves emergency egress, fire strategy, controls commissioning and electrical safety, and needs a qualified engineer with the drawings in front of them and professional indemnity insurance behind them. These notes are the layer underneath that work — enough to read a proposal critically and ask a better question. They are not a substitute for it, and nothing here should be treated as a design instruction for a specific building.

Corrections

If something here is wrong, we would rather know. Standards get revised, component behaviour changes between production runs, and we make mistakes like everyone else. Corrections that turn out to be right get made and the page's review date moves. Write to hklongtermad@gmail.com — see the contact page for what to include.

Advertising

This site carries advertising served by Google. Advertisements are not editorial: no advertiser sees or approves a page before it is published, and nothing here is a paid placement. Where we mention a component or a brand it is because it illustrates the point, not because anyone paid for the mention. How advertising affects the data collected about you is set out in the privacy policy.