Point-by-Point Photometrics

This section describes how to calculate display indoor, outdoor, and egress point-by-point photometrics.

Common Photometric Boundary Information

The values that can be specified for a photometric boundary are listed below.

Override Schedule Title: Whether or not the default calculation schedule title is to be changed for a given calculation area.

Schedule Title: The title to be used in the calculation schedule for the calculation area. This field is enabled if the Override Schedule Title box is checked.

Grid Spacing: The distance between points where footcandle levels will be calculated. See the Distance Input Format section for more information on specifying this elevation.

Floor Elevation: The elevation of the floor within the calculation area. See the Distance Input Format section for more information on specifying this elevation.

Area has a Ceiling: Whether or not an area has a ceiling.

Area has Walls: Whether or not an area has walls. If this checkbox is checked, light that is not generated inside the calculation area will affect the photometric calculations.

Wall or Ceiling Height: The height of the boundary walls or the boundary ceiling. This setting is only available if either Area has a ceiling or Boundary Obstructs Light are set. See the Distance Input Format section for more information on specifying this elevation.

Wall or Ceiling Reflectance: The percentage of light reflected by the boundary walls or the boundary ceiling. This setting is only available if either Area has a Ceiling or Area has Walls are set. It is only used if reflections are turned on in the calculation.

Top Elevation: This is the elevation at the top of the slope. See the Distance Input Format section for more information on specifying this elevation.

Bottom Elevation: This is the elevation at the bottom of the slope. See the Distance Input Format section for more information on specifying this elevation.

Common Photometric Solid Information

The values that can be specified for a photometric solid are listed below.

Starting Elevation: The elevation the photometric solid starts at. See the Distance Input Format section for more information on specifying this elevation.

If this is 0 and the object is a closed area, no values inside the object will be calculated or displayed.

If this is greater than 0, the light levels underneath the object will be calculated. This setting can be used to model overhangs.

Ending Elevation: The elevation the light-obstruction object ends at. If this elevation is lower than the elevation of a light fixture, some light will pass over the object. See the Distance Input Format section for more information on specifying this elevation.

Reflectance: The percentage of light reflected by the photometric solid. It is only used if reflections are turned on in the calculation.

Point-by-Point Photometrics Calculations

There are two types of point-by-point photometric calculations available: general and egress. Each calculation uses separate fixtures, separate fixture lumens, and separate layers.

Separate Light Fixtures: Each calculation uses a separate set of light fixtures. Each light fixture on the drawing can be marked as being included in either the general lighting calculation, egress lighting calculation, both calculations, or not included. This is important for egress calculations, where only certain light fixtures will be on during an emergency situation. See the Insert Light Fixtures section for more information on specifying whether a light fixture is used for general or egress calculations.

Separate Light Fixture Lumens: In the light fixture schedule, the total lumens for the fixture can be set differently for the general calculation and egress calculation. This is important for egress calculations for fixtures where only certain lamps will be on in an emergency situation. See the Light Fixtures section for more information on lumen settings.

Separate Layers: Light fixtures included in the egress calculation can be inserted on a separate layer from other light fixtures. The separate layer allows you to create a view of the drawing with only the egress light fixtures included. See the Layers section for more information on layers.

Multiple Areas

Multiple general and egress calculation boundaries can be defined on a single drawing. The general areas include the light from all general lights on the drawing. The egress areas include the light from all the egress lights on the drawing.

Reflections

Reflections from buildings and walls can be included in the calculation. Each wall has a reflectance value that is used to calculate the amount of light that it reflects. For outdoor photometrics, this reflection results in slightly higher values near buildings. For indoor photometrics, wall reflections are an important component of the calculation.

Reflections from the ceiling can also be included in the calculation. The ceiling height and reflectance values are set when an area is first inserted and can be modified using the Query Photometric Information command.

IES Files

The footcandle (FC) level at each point within a defined boundary is calculated using the IES file for each light fixture. See the Light Fixture Information section for more information on light fixture IES files.

General versus Egress Photometrics

There are two separate point-by-point photometric calculations: general and egress. They are calculated the same way using similar commands. There are two differences between the types of calculations.

Lumens / Lamps

Light fixtures have two settings for light output: Lumens / Lamp and Egress Lumens / Lamp. The general calculation uses Lumens / Lamp. The egress calculation uses Egress Lumens / Lamp.

The egress lumens is included separate from the regular lumens to model situations where the light uses fewer lamps in emergency mode.

General Light vs Egress Light

Light fixtures have a General Light and Egress Light checkbox. These two checkboxes control whether the light fixture is included in the corresponding calculation. Light fixtures can have one, both, or neither of these boxes checked.


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