Every desk lamp sold this year lists lumens, colour temperature and CRI. Almost none list flicker, and flicker is the thing your eyes will notice first.
What flicker actually is
An LED does not dim the way a filament does. Most dimmable LED drivers switch the light fully on and fully off, very fast, and vary the ratio — pulse-width modulation. At a high enough frequency this is invisible. At a low enough frequency it is a strobe.
The cheap way to build a dimmable driver puts that frequency somewhere in the low hundreds of hertz, which most people cannot consciously see and many people’s visual systems still respond to. The result is not “I can see it flickering.” The result is a headache at six o’clock.
How to check without an instrument
Point a phone camera at the lit surface and dim the lamp to about a quarter. If bands roll across the preview, the driver is switching slowly enough to matter. A high-frequency driver shows nothing at any dim level.
This is a rough test — a phone’s rolling shutter is not a photometer — but it separates the bad from the fine, which is the decision you are actually making in a shop.
What we do about it
The Halo runs its driver above 25 kHz at every dim level, including 1%. We are not the only lamp that does this. We are one of the few that will tell you the number.
