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Luminaire dimensions and orientation

Which way a luminaire faces in each file, and how to measure it for ten luminaire types.

Contents

The dial

The C-planes cut the luminaire like the segments of an orange. The gamma angle runs inside one plane, from straight down to straight up. An IES file uses the same kind of angles and calls them horizontal angles and vertical angles.

Every plan view on this page is seen from above. When a luminaire has a front, the front is at the top.

Plan view with C-planes and side view with gamma angles C0 C90 C180 C270 length Plan view, seen from above γ = 0°, straight down γ = 90° γ = 180° Side view, one C-plane
Left: the C-planes cut the luminaire like the segments of an orange. Right: the gamma angle runs from straight down to straight up inside one C-plane.

The 90° turn

An IES file puts the front of the luminaire at 0° (LM-63-19, definition 3.6). An LDT file puts the front at C90 (EN 13032-1, Annex D). For a road luminaire, the front is the street side.

Standard LM-63-19, definition 3.6. EN 13032-1, Annex D.

One road luminaire in an IES file, seen from above with the front at the top IES file 0° 90° 180° 270° road footpath pole One road luminaire in an LDT file, seen from above with the front at the top LDT file C90 C180 C270 C0 road footpath pole
Plan view, seen from above, with the front at the top. The curved arrow shows the direction in which the angles increase. The straight arrow is the peak beam. The same luminaire and the same light. IES puts the front at 0°. LDT puts it at C90.
Direction, on a plan seen from above with the front at the topIESLDT
Front, the street side0°C90
Left90°C180
Back, the mounting side180°C270
Right270°C0

Both formats count counterclockwise seen from above (LM-63-19, definition 3.4; LM-75-19, section 5.4.3). So a quarter turn to the left adds 90° in both.

A plain conversion keeps the angle numbers and puts the front at IES 90°. A design program then shows the luminaire turned. A calculation that needs the front, such as a BUG rating, reads the wrong side.

Two boxes and one box

An LDT file holds two boxes: the housing and the luminous area. An IES file holds one box: the luminous area. IES has no field for the housing (LM-63-19, section 5.10).

Housing and luminous area with the LDT and IES dimensions housing length (13) housing width (14) housing height (15) luminous length (16) = IES length luminous width (17) = IES width 18 C0 19 C90 20 C180 21 C270 C270 C90 Seen from below. The sides that face C180 and C270 are hidden.
LDT holds two boxes: the housing on lines 13 to 15 and the luminous area on lines 16 to 21. IES holds one box: the luminous area. The dashed faces glow.
ValueLDTIESAxis
Housing lengthline 13noneC90–C270
Housing widthline 14 (0 = round)noneC0–C180
Housing heightline 15nonevertical
Luminous lengthline 16lengthLDT C90–C270 = IES 0°–180°
Luminous widthline 17 (0 = round)widthLDT C0–C180 = IES 90°–270°
Luminous heightlines 18 to 21, one for each sideheight, one valuevertical

Units: LDT always uses mm. IES uses feet or metres.

Format guide LDT lines 13 to 21: DIALux and AGI32 EULUMDAT descriptions.

Standard IES width, length, and height: LM-63-19, sections 5.10.1 to 5.10.4, Figure 1.

The height for C0 is the height of the glowing side that faces C0. An observer on the horizon at C0 sees it. It is 0 for a flat, horizontal luminous area. No document in hand defines it. Common practice

Round or square: the IES shapes

The signs of the IES width, length, and height give the shape of the luminous opening: a negative value means round in that direction (LM-63-19, section 5.11 and Table 1).

Standard LM-63-19, section 5.11 and Table 1.

IconShapewidthlengthheight
Point 0 0 0
Rectangle W L 0
Rectangle with luminous sides W L H
Circle −D −D 0
Ellipse −W −L 0
Vertical cylinder −D −D H
Vertical elliptical cylinder −W −L H
Sphere −D −D −D
Ellipsoidal spheroid −W −L −H
Horizontal cylinder along the 0°–180° axis −D L −D
Horizontal elliptical cylinder along the 0°–180° axis −W L −H
Horizontal cylinder across the 0°–180° axis W −D −D
Horizontal elliptical cylinder across the 0°–180° axis W −L −H
Vertical circle facing the front −D 0 −D
Vertical ellipse facing the front −W 0 −H

W is a width, L is a length, H is a height, and D is a diameter.

Ten luminaire cards

All values are invented examples. LDT values are in mm. IES values are in metres, in the order width, length, height. The LDT side heights are in the order C0, C90, C180, C270.

Each card shows a plan and a side view seen from the left. The wall luminaire also has a front view. The plan is seen from above. When a luminaire has a front, the front is at the top. A dashed outline with a grey fill is the glowing part. The red lines are heights.

The mounting code comes from EN 13032-1, Annex D. An LDT file has no field for it.

Indoor

Round downlight

Mounting code C3 (EN 13032-1, Annex D)

Plan view of a round downlight, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 No front: any plane can be C0 Side view of a round downlight in the ceiling Side view housing 110 mm glowing height 0 ceiling housing 200 mm lens 150 mm
ValueIn the fileSource
Orientation Any plane can be C0 Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 200 / 0 / 110 Format guide Width 0 means round
LDT luminous area, lines 16 and 17 150 / 0 Format guide Width 0 means round
LDT side heights, lines 18 to 21 0 / 0 / 0 / 0 Common practice
IES width, length, height −0.15 −0.15 0 (circle) Standard LM-63-19, Table 1

Watch out. The IES size is the lens (150 mm), not the housing (200 mm).

Square panel 600 × 600

Mounting code C6 (EN 13032-1, Annex D)

Plan view of a square panel, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 Side view of a square panel under the ceiling, seen from the left Side view from the left 40 mm glowing height 0 ceiling IES 0° edge IES 180° edge
ValueIn the fileSource
Orientation The maker marks C0 Standard EN 13032-1, Annex D. Which edge is C0 is common practice.
LDT housing, lines 13 to 15 595 / 595 / 40 Format guide EULUMDAT descriptions
LDT luminous area, lines 16 and 17 580 / 580 Format guide EULUMDAT descriptions
LDT side heights, lines 18 to 21 0 / 0 / 0 / 0 Common practice
IES width, length, height 0.58 0.58 0 (rectangle) Standard LM-63-19, Table 1

Watch out. A width of 0 makes a program draw a round panel. A square needs both numbers.

Linear pendant, up and down light

Mounting code C6 (EN 13032-1, Annex D)

Plan view of a linear pendant, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 Side view of a linear pendant with up and down light, seen from the left Side view from the left 80 mm glowing side 30 mm ceiling up light down light IES 0° end IES 180° end
ValueIn the fileSource
Orientation Long axis along C90–C270 Standard EN 13032-1, clause 4.2.3
LDT housing, lines 13 to 15 1200 / 60 / 80 Format guide EULUMDAT descriptions
LDT luminous area, lines 16 and 17 1150 / 50 Format guide EULUMDAT descriptions
LDT side heights, lines 18 to 21 30 / 0 / 30 / 0 Common practice
IES width, length, height 0.05 1.15 0.03 (rectangle with luminous sides) Standard LM-63-19, Table 1. IES has one height for all four sides. LDT can say that the ends are dark.

Watch out. Both formats hold one luminous area. Give the lower opening. The uplight is in the light data, above 90°, not in the dimensions.

Outdoor

Road luminaire

Mounting code C1 (EN 13032-1, Annex D)

Plan view of a road luminaire, seen from above with the front at the top Front IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 pole Side view of a road luminaire on a pole arm, seen from the left Side view from the left 90 mm glowing height 0 arm pole front: street side back
ValueIn the fileSource
Orientation C90 crosses the road. IES 0° is the street side. Standard EN 13032-1, Annex D. LM-63-19, definition 3.6. TM-15-20, section 3.3.
LDT housing, lines 13 to 15 600 / 250 / 90 Common practice Length along the arm
LDT luminous area, lines 16 and 17 400 / 200 Format guide EULUMDAT descriptions
LDT side heights, lines 18 to 21 0 / 0 / 0 / 0 Common practice
IES width, length, height 0.2 0.4 0 (rectangle) Standard LM-63-19, Table 1

Watch out. A plain conversion puts the street side at IES 90°. A BUG rating then reads the wrong side.

Floodlight

Mounting code C2 (EN 13032-1, Annex D)

Plan view of a floodlight aimed straight down, seen from above with the front at the top Front IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 bracket Side view of a floodlight aimed straight down, seen from the left Side view from the left 100 mm glowing height 0 bracket mast aimed straight down front back
ValueIn the fileSource
Orientation C270 through the bracket. C90 is the front. Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 300 / 280 / 100 Format guide EULUMDAT descriptions
LDT luminous area, lines 16 and 17 260 / 240 Format guide EULUMDAT descriptions
LDT side heights, lines 18 to 21 0 / 0 / 0 / 0 Common practice
IES width, length, height 0.24 0.26 0 (rectangle) Standard LM-63-19, Table 1. Annex D: the sizes apply with the floodlight aimed straight down.

Watch out. LDT has no place for Type B data. A Type B file exists only as IES (photometric type 2). Tilt during the test goes on LDT line 25.

Wall luminaire, round glowing front

Mounting code C2 (EN 13032-1, Annex D)

Plan view of a wall luminaire, seen from above with the front at the top Front IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 wall Front view of a wall luminaire with a round glowing front Front view glowing front 200 mm Side view of a wall luminaire, seen from the left Side view from the left glowing front 200 mm wall front
ValueIn the fileSource
Orientation C270 to the wall. C90 away from it. Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 120 / 200 / 200 Format guide EULUMDAT descriptions
LDT luminous area, lines 16 and 17 0 / 200 Common practice LDT has no round flag for a vertical face
LDT side heights, lines 18 to 21 0 / 200 / 0 / 0 Common practice LDT has no round flag for a vertical face
IES width, length, height −0.2 0 −0.2 (vertical circle facing the front) Standard LM-63-19, Table 1

Watch out. An LDT program draws the round front as a 200 × 200 square.

Glowing shapes

Cylinder pendant, glowing sides

Mounting code C3 (EN 13032-1, Annex D)

Plan view of a cylinder pendant, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 No front: any plane can be C0 Side view of a cylinder pendant with glowing sides Side view glowing sides 300 mm ceiling
ValueIn the fileSource
Orientation Any plane can be C0 Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 150 / 0 / 300 Format guide Width 0 means round
LDT luminous area, lines 16 and 17 150 / 0 Format guide Width 0 means round
LDT side heights, lines 18 to 21 300 / 300 / 300 / 300 Common practice
IES width, length, height −0.15 −0.15 0.3 (vertical cylinder) Standard LM-63-19, Table 1

Watch out. The IES height is positive and the width and length are negative. That is the vertical cylinder of Table 1.

Globe

Mounting code C3 (EN 13032-1, Annex D)

Plan view of a globe, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 No front: any plane can be C0 Side view of a globe pendant Side view glowing 300 mm ceiling
ValueIn the fileSource
Orientation Any plane can be C0 Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 300 / 0 / 300 Common practice LDT has no sphere shape
LDT luminous area, lines 16 and 17 300 / 0 Common practice LDT has no sphere shape
LDT side heights, lines 18 to 21 300 / 300 / 300 / 300 Common practice LDT has no sphere shape
IES width, length, height −0.3 −0.3 −0.3 (sphere) Standard LM-63-19, Table 1

Watch out. IES has a sphere shape. LDT has none, and a program draws a box or a cylinder.

Bollard

Mounting code C3 (EN 13032-1, Annex D)

Plan view of a bollard, seen from above IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 No front: any plane can be C0 Side view of a bollard with a glowing band Side view 900 mm glowing band 100 mm ground
ValueIn the fileSource
Orientation Round optic: any plane can be C0 Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 200 / 0 / 900 Format guide Width 0 means round
LDT luminous area, lines 16 and 17 180 / 0 Format guide Width 0 means round
LDT side heights, lines 18 to 21 100 / 100 / 100 / 100 Common practice
IES width, length, height −0.18 −0.18 0.1 (vertical cylinder) Standard LM-63-19, Table 1

Watch out. For a one-sided optic, the front is C90 in LDT and 0° in IES. Only the C90 height is set.

Spotlight

Track spotlight

Mounting code C2 (EN 13032-1, Annex D)

Plan view of a track spotlight aimed straight down, seen from above with the front at the top Front IES 0° · LDT C90 IES 180° · LDT C270 IES 90°LDT C180 IES 270°LDT C0 track Side view of a track spotlight aimed straight down, seen from the left Side view from the left 150 mm glowing height 0 track adapter front back
ValueIn the fileSource
Orientation C270 through the track adapter Standard EN 13032-1, Annex D
LDT housing, lines 13 to 15 80 / 0 / 150 Format guide Width 0 means round
LDT luminous area, lines 16 and 17 70 / 0 Format guide Width 0 means round
LDT side heights, lines 18 to 21 0 / 0 / 0 / 0 Common practice
IES width, length, height −0.07 −0.07 0 (circle) Standard LM-63-19, Table 1. Section 5.10: the sizes apply with the spot aimed straight down.

Watch out. The file holds the spot aimed straight down. The design program aims it. A tilt during the test goes on LDT line 25.

The XML format swaps length and width

TM-33-23 puts the length on the other axis

TM-33-23 is the IES XML format that replaces LM-63. It puts width along 0°–180° and length along 90°–270° (TM-33-23, section 3.3 and Figure 3-1). That is the opposite of an IES file. It also holds colour.

A value copied from an IES file into a TM-33 file must swap length and width.

How to measure: a checklist

  1. Find the mounting: ceiling, pendant, wall, pole, track, or ground.
  2. Find the front. Mark it IES 0° and LDT C90. A round luminaire has no front.
  3. For a luminaire with no front, find the long axis. It lies along IES 0°–180° and LDT C90–C270.
  4. Measure the housing for LDT lines 13 to 15. Use 0 for the width of a round housing.
  5. Measure only the glowing part for LDT lines 16 and 17 and for the IES width and length.
  6. Measure the glowing height of each side. Enter 0 for a side that does not glow.
  7. Convert the units: mm for LDT, metres or feet for IES. Make an IES value negative for a round direction.

Sources