# Sunrise/sunset ramp

> A sunrise/sunset ramp is a programmed gradual rise and fall of fixture intensity at the start and end of the light period, adding hours of light but little DLI.

- Canonical: https://genetixbay.com/knowledge/glossary/sunrise-sunset-ramp.html
- Also written: sunrise sunset, light ramping, dimmer ramp, dawn dusk simulation, ramp up ramp down, sunrise mode
- Glossary category: Environment and light · Evidence: Grower practice
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A sunrise/sunset ramp is a controller setting that brings a dimmable fixture (usually [LED](https://genetixbay.com/knowledge/glossary/led.md)) up from off to full power over a set time, and back down at the end of the day. Ramps of 15–60 minutes are common. They imitate the gradual dawn and dusk plants evolved with.

## In practice

Ramps soften the sudden switch from darkness to full intensity, which gives [stomata](https://genetixbay.com/knowledge/glossary/stomata.md) and [leaf temperature](https://genetixbay.com/knowledge/glossary/leaf-temperature.md) time to adjust and avoids a sudden spike in room heat and humidity load. They also reduce inrush on the electrical supply.

They add very little light. A 30-minute linear ramp to 900 [µmol/m²/s](https://genetixbay.com/knowledge/glossary/ppfd.md) delivers on average 450 µmol/m²/s for half an hour, about 0.8 [mol/m²/day](https://genetixbay.com/knowledge/glossary/dli.md), so two ramps add about 1.6 mol/m²/day. This is why the founder's [13/11](https://genetixbay.com/knowledge/glossary/13-11.md) practice amounts to roughly 12 hours of high intensity, with ramps making up the rest.

Count ramp time as light time for flowering purposes: plants sense even dim light as day. If you add 1-hour ramps to a [12/12](https://genetixbay.com/knowledge/glossary/12-12.md) schedule, your real night is now 10 hours, which some cultivars will not tolerate.

## Don't confuse with

- **13/11**: a schedule; ramps are one way to fill its extra hour.
- **Light leak**: unplanned light during the dark period.

## Myth check

Ramps are *Grower practice*; there is little controlled cannabis evidence of a yield effect either way. Their value is in smoother transitions and control.

## Related terms

[13/11](https://genetixbay.com/knowledge/glossary/13-11.md), [12/12](https://genetixbay.com/knowledge/glossary/12-12.md), [DLI](https://genetixbay.com/knowledge/glossary/dli.md), [LED](https://genetixbay.com/knowledge/glossary/led.md)

## Read more

- [Photoperiod and light leaks: 18/6, 12/12 and the dark period](https://genetixbay.com/knowledge/environment/photoperiod-light-leaks.md)