A one-metre bar built to cover a full shelf. Where the SF300 lights one tray, the SF600 covers two end to end, which makes it the natural format for a serious spring nursery or for sustained microgreen production.

The most important number on this page is 2.3 µmol/J. That's efficacy: the number of useful photons produced for each joule of electricity consumed. It's the measure that determines what you'll pay Hydro for a given quantity of light, and it's the one cheap lamp makers never publish. For reference, old high-pressure sodium lamps ran around 1.7 µmol/J, and entry-level “blurple” panels often sit below 1.5. At 2.3, the SF600 is among the efficient bars, and over a three-month seedling season the gap shows up on the bill.

The spectrum is full and detailed: 660-665 nm for deep red, chlorophyll's absorption peak; 730-740 nm for far red, which acts on elongation and on day-night cycle signalling; 2800-3000 K for warm white; 4800-5000 K for cool white rich in blue, the one that keeps seedlings compact instead of letting them stretch. The 384 OSRAM diodes spread that light along the whole length, which avoids the central hot spot of panel lamps.

What it covers: 60 cm × 120 cm, or 2' × 4'. Its 3.5 cm thickness lets it mount under a standard shelf.

• Measures 100 cm × 15 cm × 3.5 cm. 384 OSRAM LEDs.
• Covers 60 cm × 120 cm (2' × 4').
• Power draw: 74 W. Efficacy: 2.3 µmol/J.
• Full spectrum: 660-665 nm (red), 730-740 nm (IR), 2800-3000 K (white), 4800-5000 K (blue).
• Suited for: a spring nursery, microgreens in production, shelf mounting.