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Extech LT45 Review: LED Light Meter for Modern Lighting

The Extech LT45 is a light meter designed for the LED era, with settings for coloured LED sources and a range wide enough for direct sunlight. This review explains why coloured LEDs need special handling, what the 400,000 lux range is for, and warns that the Amazon listing bullets belong to a clamp meter.

By the Akermin Editorial Team · 4 min read

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Extech LT45 Review: LED Light Meter for Modern Lighting

Extech · Extech LT45 Color LED Light Meter, Lux and Foot Candle, 400000 Lux

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Price and availability are shown on Amazon and can change at any time.

Verdict

The LT45 answers two problems that a conventional light meter has with modern lighting. The first is coloured LEDs: the narrow-band emission of a red, blue or green LED falls where a standard colour-corrected sensor is least accurate, so a grow light, a stage wash or a signage panel reads wrong. The LT45 provides selectable settings for common LED colours as well as standard light. The second is range: at 400,000 lux it measures direct sunlight and light close to high-output fixtures that would over-range a 40,000 lux meter such as the LT300. A warning about the Amazon listing: its bullets describe a clamp meter, so we have relied on the title and Extech’s documentation. For horticulture, signage, stage and outdoor work it is the more capable meter; for ordinary office and workplace audits the LT300 is simpler.

Who It Is For

  • Horticultural growers measuring under coloured and full-spectrum LED grow lights.
  • Signage, display and stage technicians working with coloured LED sources.
  • Anyone who needs to measure daylight and direct sun as well as indoor light.

Documented Specifications

Item Documentation
Units Lux and foot-candles
Range Up to 400,000 lux
Light types Selectable settings for common LED colours plus standard white light (Extech documentation)
Listing note Amazon bullets describe a clamp meter; title and Extech datasheet used

About the Listing

The Amazon title reads correctly as the Extech LT45 Color LED Light Meter with lux and foot-candle units and a 400,000 lux range. The four feature bullets, however, describe True RMS measurement, a flexible 10 in clamp jaw and a 7.5 mm cable diameter, which belong to a flexible clamp meter. As with other older Extech listings, confirm the model on the box and download the datasheet. Nothing in this review is taken from those bullets.

Why Coloured LEDs Need Their Own Settings

A light meter’s colour correction filter shapes the sensor’s response to match the eye across the visible spectrum, but the match is approximate and worst at the deep red and blue ends. A white LED spreads its energy across the spectrum and reads acceptably. A red or blue LED concentrates its energy in a narrow band exactly where the filter’s error is largest, so a standard meter can be off by a large margin. The LT45’s LED colour settings apply a correction for each colour, bringing the reading back toward true illuminance. Growers who compare a standard meter with the LT45 under red and blue grow lights report substantial differences, which is the reason the meter exists. Our guide to choosing a light meter covers the sensor physics.

The 400,000 Lux Range

Direct summer sunlight exceeds 100,000 lux. Light within a few centimetres of a high-output horticultural fixture can also be very bright. A meter that stops at 40,000 lux simply reads over-range in those situations. The LT45’s range allows daylight surveys, sun-versus-shade comparisons on a site, and measurements close to fixtures. At the low end it still reads ordinary room light, so it doubles as a general meter.

Lux Is Not PPFD

For plant growth the relevant measure is photosynthetic photon flux density, which counts photons across the range plants use rather than weighting for the human eye. The LT45 measures illuminance in lux, corrected for LED colour, which is useful for comparing fixtures and checking uniformity but is not a PPFD measurement. Growers who need PPFD use a quantum sensor. This distinction is worth understanding before buying a lux meter for horticulture.

Strengths

  • Correction settings for coloured LED sources.
  • Range to 400,000 lux for daylight and high-output fixtures.
  • Reads ordinary white light as well.

Limitations

  • Amazon listing bullets belong to a different product.
  • Lux, not PPFD; not a quantum sensor.
  • More settings to get right than a basic meter.

How It Compares

The Extech LT300 is the simpler general-purpose meter with a remote sensor and a 40,000 lux range. The Extech 407026 has corrections for sodium and mercury discharge lamps rather than LEDs and a PC interface. The Extech EN300 includes a basic light function. Choose the LT45 when coloured LEDs or very bright sources are the job.

How We Research

This review is based on Extech’s published documentation for the LT45, the Amazon listing title (the bullets describe a different product), and owner reports. We did not run laboratory tests.

Extech LT300 Light Meter, Remote Sensor, Peak and Relative Modes

Extech LT300 Light Meter, Remote Sensor, Peak and Relative Modes

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Extech 407026 Heavy Duty Light Meter, Lux/Foot-Candle, RS-232, 4 Modes

Extech 407026 Heavy Duty Light Meter, Lux/Foot-Candle, RS-232, 4 Modes

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Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.

Frequently Asked Questions

Why do the Amazon bullets talk about a clamp jaw and True RMS?

The feature bullets on the listing describe a clamp meter, not the LT45. The title correctly identifies the LT45 as a colour LED light meter with a 400,000 lux range. We used the title and Extech documentation.

What are the LED colour settings for?

Coloured LEDs emit narrow bands of light that a standard colour-corrected sensor reads incorrectly. The LT45 provides settings that apply a correction for common LED colours so the reading is closer to true illuminance.

Why 400,000 lux?

Direct summer sunlight exceeds 100,000 lux and horticultural lighting close to the fixture can be very bright. The wide range lets the LT45 measure outdoors and at grow lights where a 40,000 lux meter over-ranges.

Does it also measure ordinary white light?

Yes. Extech documents a standard setting for white light and daylight alongside the LED colour settings.

Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.