Sweep your camera over the canopy and see where the light map might be wrong.
Light Sweep compares relative brightness across a few canopy points — read through your camera against a white reference card — to what GrowScope's own 3D light map predicts for those same points, anchored to one PPFD reading you already trust from a real meter. It's a diagnostic for where the two disagree, not a replacement for a PAR meter.
The problem
A phone camera is not a quantum sensor — it has no idea how many photons in the 400–700nm range actually hit it. It auto-exposes to make every scene look reasonably lit, which erases the very brightness differences you're trying to compare, and a lamp's spectrum — especially a 'blurple' one — skews the color channels a plain photo relies on.
Why it's hard to solve alone
Your light map is a physical model calibrated by whatever PPFD readings you've entered — but if you only ever measure one or two points, its confidence about the rest of the canopy is only as good as its assumptions about your walls, your lamp, and your layout. A quick camera sweep across more points, even at lower precision, can catch a spot where the model and reality have quietly drifted apart — a lamp that shifted, a reflective surface that changed, a plant that grew into its own shadow.
How GrowScope helps
You anchor the sweep with one PPFD reading you trust from a real meter, then move your camera to a few more canopy points with a white reference card in frame. GrowScope only turns that into a number when it actually knows the exposure — locked manually on Chrome for Android, or read from a photo's EXIF data on iPhone — because without a known exposure the camera has already silently re-adjusted the very brightness you're trying to measure. Where exposure isn't known at all, it tells you so instead of showing a misleading number.
How it works
- Enter one PPFD reading from a real meter at a reference point — Light Sweep anchors every other point to it, it never replaces it.
- On Chrome for Android, Light Sweep locks manual camera exposure so every point is captured under the same conditions — confirmed against the camera's own reported settings, not assumed.
- On iPhone, where the web has no manual exposure control, you take a photo with the system camera and pick it from your library; Light Sweep reads its EXIF exposure data and honestly tells you when a photo doesn't carry it.
- With no known exposure at all, Light Sweep shows no numbers rather than a comparison the auto-exposed camera has already quietly distorted.
- The tolerance is stated plainly with the result — about ±20% with a locked exposure, ±35% from EXIF — and a mismatch beyond that is flagged as a diagnostic worth a real re-measurement, not folded automatically into your light map's calibration.
What you get
You find out where your light map and your actual canopy have drifted apart, with an honest tolerance attached to every number — and you always know exactly which mode produced it.
Frequently asked questions
Can Light Sweep replace a PAR meter?
No — it needs one trusted PPFD reading from a real meter as its anchor, and its own numbers carry a stated ±20–35% tolerance, well short of meter accuracy. It's built to catch where your light map and the real canopy disagree, not to replace the meter that calibrates the map in the first place.
Why does it sometimes show no numbers at all?
Because a phone camera auto-adjusts brightness to whatever it's pointed at. Without a known, fixed exposure — locked manually or read from a photo's EXIF data — comparing brightness between two points would compare two different auto-exposure decisions, not two different light levels. GrowScope would rather show nothing than a number that's quietly wrong.
Does this work the same on iPhone and Android?
Not quite — Chrome for Android can lock manual camera exposure directly, which gets the tighter ±20% tolerance. iPhone's web camera has no manual exposure control, so Light Sweep instead reads exposure from a photo's EXIF data taken with the system camera, at a wider ±35% tolerance.
Does a Light Sweep result recalibrate my light map automatically?
No — it's a diagnostic, shown alongside the model, not fed back into it automatically. A real disagreement is a prompt to take an actual PPFD reading at that spot, not a silent correction to the map.