Extech LT300

The LT300 is the meter to buy if you want one tool that you can trust for every circadian job: confirming a SAD lamp’s 10,000 lux, checking how much light reaches you at a desk, and reading daylight outdoors. Its two features that matter most are ones budget meters skip or leave unstated: cosine and color correction, and a sensor on a cable.

Cosine correction means light arriving at an angle, from a side window or a ceiling panel, is weighted properly rather than under-read. Color correction means the sensor is filtered to follow the eye’s sensitivity curve more closely, which should shrink the error swing between LED types that cheaper meters show. Extech does not publish cosine or spectral error figures for the LT300, so treat the ±5% basic accuracy as the number to rely on.

The sensor sits on a 30 cm coiled cable that stretches to 61 cm. That lets you hold the sensor at eye height, facing the lamp, while you read the display from the side. With a built-in sensor, your hand and head tend to block part of the light.

The 400,000 lux ceiling is more than any outdoor reading needs, and 0.01 lux resolution covers dim evening levels too.

What it does not do is tell you about spectrum. Like every lux meter, it weights light by brightness to the eye, not by its effect on melanopsin. Under warm white LEDs, the melanopic value is roughly half the lux reading. If you need melanopic numbers directly, the UPRtek MK350S Premium reports them, at about 17 times the price.

Against the Extech LT45, the LT300 is $115 cheaper with a looser ±5% spec. For checking lamps and rooms, that difference rarely changes a decision.