Digital Stealth Care · light
PPFD chart by growth stage
PPFD is how much light reaches the canopy at one moment, in micromoles per square metre per second. DLI is the day's total, in moles per square metre per day. This DLI and PPFD chart turns the stage bands DSC uses into the PPFD that reaches them, for each stage's light hours.
309 to 617
µmol/m²/s, the PPFD for the vegetative DLI band over 18 hours of light
694 to 926
µmol/m²/s, the same for flowering over 12 hours, without added CO₂
1,273
µmol/m²/s, the top of the flowering band, which only pays with added CO₂
The chart
PPFD by growth stage
Find your stage on the left. The DLI band is the daily light the stage aims for, and the PPFD is what your canopy needs, steadily, while the lights are on, to deliver it in that stage's hours.
| Stage | Light hours | DLI, mol/m²/day | PPFD, µmol/m²/s |
|---|---|---|---|
| Seedling, germination and rooting | 18 | 10 to 20 | 154 to 309 |
| Vegetative: early, vegetative and late push | 18 | 20 to 40 | 309 to 617 |
| Early flowering and flowering | 12 | 30 to 40 | 694 to 926 |
| Late flowering and the final 48 to 72 hours | 12 | 40 to 50 | 926 to 1,157 |
| Any flowering stage with added CO₂ | 12 | 35 to 55 | 810 to 1,273 |
Rounded to the nearest whole number. These are generic stage bands, not tuned to a strain, and not a reading from a light meter. The hours are the default light hours on DSC's stage rail (18 for seedling and vegetative stages, 12 for flowering), and every row can be edited.
The arithmetic
How a DLI becomes a PPFD
Every row above comes from one line of arithmetic, so you can check it or redo it for your own light hours.
PPFD = DLI × 1,000,000 ÷ (hours × 3,600)
There are 3,600 seconds in an hour, and a mole is 1,000,000 micromoles. Hours of light times 3,600 is the seconds the light is on, so dividing the day's moles by those seconds gives the steady rate that adds up to the DLI.
For example, the low end of the vegetative band is 20 mol/m²/day. Over 18 hours that is 20 × 1,000,000 ÷ (18 × 3,600) = 309 µmol/m²/s.
The same DLI over a shorter day needs a higher PPFD. Flowering runs 12 hours of light, so each DLI there needs a higher PPFD than the same DLI over the 18 hour vegetative day.
Read this before you chase a number
What these numbers are, and are not
Generic stage bands
The DLI bands are the generic ones DSC uses to say whether a tent's light is under, in band or over. They are not tuned to a strain, and the plant decides what it can use. Strains only change flowering time, stage and the harvest window in DSC.
CO₂ changes the flowering band
Without added CO₂, a flowering canopy cannot use the top of the flowering band. DSC aims for 30 to 40 mol/m²/day through bulk flower and 40 to 50 late in flower. With added CO₂ the band is 35 to 55, and its top needs about 1,273 µmol/m²/s over 12 hours. The CO₂ supplemented setting is off by default.
In the app
Your lamp's own map beats a generic chart
A chart like this one tells you what a stage asks for. What your lamp actually delivers depends on the lamp, how high it hangs and how far it is dimmed.
DSC matches each lamp to a fixture in DSC-KitLib. Where the lamp maker has published a PPFD map, DSC reads it: the maker's map at your canopy distance, scaled by the dim level and multiplied by the hours the lamp is on, gives a running and projected DLI for the tent. It is labelled maker map everywhere, because it is an estimate and not a PAR meter.
If you have not entered a canopy distance, DSC reads the map at the maker's recommended hang height for the stage and says so. Where the library has the fixture but not its map yet, the card says that too.
DSC then compares that DLI with the generic band for the stage and says whether it is under, in band or over. When it is not in band, one line says what would reach it: a dim level, a canopy distance, or hours of light (never hours in flower). It is advice only.
The Light desk guide shows the DLI estimate and the PPFD map card, and how DLI is estimated lists what goes into it. The supported devices page lists the grow lights DSC recognises.
Light and climate together
Light is half of the room
Light is one input to the room. Temperature and humidity are the others, and the free VPD calculator turns that pair of readings into the number growers steer by.
Every alpha build is free, this one included, and yours to keep. No account, no subscription, no licence check. Keep the image and you keep the software.