Height vs. PPFD Penetration Into Canopy

The height of the grow light has a significant effect on the depth of irradiance (PPFD) penetration below the canopy top.

The following tables illustrate how keeping the irradiance at the top of the canopy at 500 µmol/m²/s and varying the grow light height affects the level of irradiance into the canopy. Inch by inch.

The height of the grow light should be increased as the canopy gets higher. The intensity of the LEDs should be adjusted for each height.

As the height of the grow light over the canopy is decreased so does the depth of penetration into the canopy (keeping the intensity of the grow light constant at the top of the canopy).

Height=40

D	ppfd	%
0	500	100
1	476	95
2	454	91
3	433	87
4	413	83
5	395	79
6	378	76
7	362	72
8	347	69
9	333	67
10	320	64
11	308	62
12	296	59

Height=35

D	ppfd	%
0	500	100
1	473	95
2	447	89
3	424	85
4	403	81
5	383	77
6	364	73
7	347	69
8	331	66
9	316	63
10	302	60
11	289	58
12	277	55

Height=30

D	ppfd	%
0	500	100
1	468	94
2	439	88
3	413	83
4	389	78
5	367	73
6	347	69
7	329	66
8	312	62
9	296	59
10	281	56
11	268	54
12	255	51

Height=25

D	ppfd	%
0	500	100
1	462	92
2	429	86
3	399	80
4	372	74
5	347	69
6	325	65
7	305	61
8	287	57
9	270	54
10	255	51
11	241	48
12	228	46

Height=20

D	ppfd	%
0	500	100
1	454	91
2	413	83
3	378	76
4	347	69
5	320	64
6	296	59
7	274	55
8	255	51
9	238	48
10	222	44
11	208	42
12	195	39

Height=15

D	ppfd	%
0	500	100
1	439	88
2	389	78
3	347	69
4	312	62
5	281	56
6	255	51
7	232	46
8	213	43
9	195	39
10	180	36
11	166	33
12	154	31

Height=10

D	ppfd	%
0	500	100
1	413	83
2	347	69
3	296	59
4	255	51
5	222	44
6	195	39
7	173	35
8	154	31
9	139	28
10	125	25
11	113	23
12	103	21

Height=5

D	ppfd	%
0	500	100
1	347	69
2	255	51
3	195	39
4	154	31
5	125	25
6	103	21
7	87	17
8	74	15
9	64	13
10	56	11
11	49	10
12	43	9

As the "Height From" is decreased to "To Height" the intensity at the top of the canopy is adjusted to the PPFD entered.

Column Descriptions
D = Depth, distance below the top of the canopy
ppfd=Irradiance at that depth
%=Percentage difference between PPFD at that depth comparded to the PPFD at the top of the canopy.
Increment = Increments that the Height is decreased.

Input Descriptions
Height From: Starting height above canopy. Must be greater than "To Height".
To Height: Ending height. From and To define the range of heights to view.
Increment: set to 1 to see all heights in your selected range. Increase to skip some.
PPFD: The desired PPFD at the top of the canopy.
Max Depth: How many inches into the canopy you want to view.