Best for melanopic light · Light meters

UPRtek MK350S Premium

by UPRtek

Handheld spectrometer that reports melanopic lux alongside lux, color temperature, CRI and flicker. The only meter here that reads body-clock light directly.

Specs

Range1–150,000 lux
AccuracyJIS Class AA, DIN Class B
Cosine correctedNot stated
Melanopic readingYes (melanopic lux)
SensorBuilt-in spectrometer
Spectral range380–780 nm, 1 nm steps
BandwidthAbout 12 nm
Other metricsCCT, CRI, TM-30, flicker, blue light hazard
Display4.3-inch touchscreen
BatteryRechargeable, up to 4 hours
Weight260 g
Data exportExcel and JPG

Specs from the manufacturer and the sources listed below. Last verified Oct 20, 2026.

Good

  • Shows melanopic lux on screen, so there is no need to export spectra and calculate
  • Full 380 to 780 nm spectrum at 1 nm steps, exportable to Excel
  • Flicker metrics (percent flicker, flicker index, IEEE 1789 risk) for checking lamps and dimmers
  • Conforms to JIS Class AA and DIN Class B, according to US distributor Gamma Scientific

Not so good

  • $4,125, about 17 times the Extech LT300
  • Reports melanopic lux (the WELL unit), not CIE S 026 melanopic EDI; divide by about 1.10 to convert
  • Battery lasts up to 4 hours per charge
  • Sold through resellers, not direct; price is by quote on UPRtek's site

A lux meter tells you how bright light looks. A spectrometer records the full spectrum and can weight it any way you like, including by the melanopsin sensitivity curve that matters for the body clock. The MK350S Premium is the one meter here that does that weighting on the spot and lists “Melanopic Lux” among its readings.

That matters because the 2022 expert consensus on indoor light gives its targets in melanopic units, not lux: at least 250 during the day, at most 10 in the evening (Brown 2022). With a lux meter you have to guess the conversion from bulb color. With this, you read it.

One catch: the MK350S reports melanopic lux, the older unit used by the WELL building standard. The consensus targets use melanopic EDI from the CIE S 026 standard. A Lawrence Berkeley and Pacific Northwest National Laboratory paper gives the conversion as melanopic EDI = melanopic lux / 1.103. So a reading of 275 melanopic lux is about 250 melanopic EDI.

Beyond melanopic light, it measures color temperature, CRI and TM-30 color fidelity, blue light hazard and flicker. Flicker is a useful extra when checking cheap LED bulbs or dimmers.

UPRtek does not publish an illuminance accuracy figure on its product page. Its US distributor states conformance with JIS Class AA and DIN Class B, the same classes as the Konica Minolta T-10A reference lux meter.

For most people this is far more instrument than needed. A lux meter like the Extech LT300, plus the rule that warm white LEDs give about half their lux as melanopic EDI, gets close enough for home use. Buy this if you design lighting, run studies, or want numbers you can compare directly against published targets.

Sources

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