IES files contain 3 number for luminaire luminous length, width and height.
By changing sign or setting to zero more shapes than rectangular can be described.
In the standard for IES files for 2001 and later the definitions changed.
Below is a comparison.
Differences between 1995 and before and 2001 and later IES files.
| width | length | height | IES1995 and before | IES2001 and later | |
| 0 | 0 | 0 | point | point |
| +w | +l | 0 | rectangular (implied) | rectangular |
| +w | +l | +h | rectangular (default) | rectangular with sides |
| -d | 0 | 0 | circular | UNDEFINED |
| -d | -d | 0 | UNDEFINED | circular |
| -d | -d | +h | UNDEFINED | vertical circular cylinder |
| -d | 0 | +h | vertical circular cylinder | UNDEFINED |
| -w | -l | 0 | UNDEFINED | ellipse |
| -w | -l | +h | UNDEFINED | vertical ellipsoid cylinder |
| -d | -d | -d | UNDEFINED | sphere |
| -w | -l | -h | UNDEFINED | ellipsoidal spheroid |
| -d | +l | -d | UNDEFINED | horizontal circular cylinder along photometric horizontal |
| 0 | +l | -d | horizontal circular cylinder along photometric horizontal | UNDEFINED |
| -w | +l | +h | ellipse allong luminaire length | UNDEFINED |
| -w | +l | -h | ellipsoid along luminaire length | horizontal ellipsoidal cylinder along photometric horizontal |
| +w | 0 | -d | horizontal circular cylinder perpendicular to photometric horizontal | UNDEFINED |
| +w | -d | -d | UNDEFINED | horizontal circular cylinder perpendicular to photometric horizontal |
| +w | -l | +h | ellipse cylinder along luminaire width | UNDEFINED |
| +w | -l | -h | ellipsoid along luminaire width | horizontal ellipsoidal cylinder perpendicular to photometric horizontal |
| -d | 0 | -d | sphere | vertical circle facing photometric horizontal |
| -w | 0 | -h | UNDEFINED | vertical ellipse facing photometric horizontal |
