Tutorial for the use of the Innerscene Virtual Sun A7 LDT and IES files

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This article is intended for professional lighting designers who use light modeling packages such as Dialux or Relux. We provide options to model Innerscene Virtual Sun Model A7 in models for light level studies and/or visualization of both intensity and CCT within an environment.

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The LDT and IES files of the Innerscene A7 lighting fixture are synthetically generated. Measured photometric data is expected to be available in the future, however results of lighting simulations with the synthesized photometrics have been verified with “in field measurements” and have proven the synthesized photometrics to be within a margin of +-10%. We have had to slightly expand the sun beam divergence angle in the IES & LDT files because light simulation packages were not designed to handle this type of light fixture.

LDT files and IES files linked above are available for your renderings and simulations. If your software allows for the use of LDT files we suggest you use the LDTs, as these also include the respective correlated color temperature (CCT) of the lighting unit.

IES files do not allow you to specify CCT in the file format. Using the IES files you can still manually adjust the CCT to the correct values in your software if your software allows it.

The Innerscene A7 lighting fixture produces two types of light outputs which have different CCTs, luminous flux, and beam angles.

Sun light:

  • CCT of 4500K (fixed)
  • Beam angle divergence of less than 2 degrees
  • Beam direction is 30 degrees from nadir
  • Luminous flux of ~1080 lumens

Sky light:

  • Adjustable CCT ranges from 3000K to 15000K following the daylight locus
  • Diffuse illumination with Lambertian distribution
  • Luminous flux of ~5670 lumens

For modeling purposes we have provided two options:

Option 1 – Combined sun and sky light outputs as a single IES / LDT file

This is an easy option can be used if you only care about lux levels for light level studies

Option 2 – Separate sun and sky IES / LDT files

This option is more appropriate for visualization purposes where room CCTs are needed.

Lighting simulation using combined sun & sky photometric files

If you need to generate a lighting simulation with emphasis on the correct lighting levels and the appearance of a 3D render in the simulation is not as important, you might want to use the combined photometric files which can easily be imported into Dialux or other as a single IES / LDT file.

These files (A7-combined.*) have both lighting distributions incorporated into one photometric file. This is easier to handle in the software and will reduce the occurrence of software bugs. This approach will lead to correct lighting levels and lighting distribution. The combined file, however, can handle only one correlated color temperature for the combined lighting distribution. The resulting render would look similar to these where the sun and the sky light have the same CCT.

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Visualization of CCT using separate sun & sky IES / LDT files

If you want to produce a visualization of the effect of using the Innerscene A7 lighting fixture in a room, modeling the different CCTs of the sun light and the sky light are crucial. For this scope the two lighting effects (SUN and SKY) have been separated into two files (A7-SUN.* and A7-SKY.*) and given their respective CCTs. The two files will be placed in your simulation or rendering geometry one over the other, in the exact same position. The reason for this procedure is that neither LDT nor IES files can cope with two different CCTs in one single lighting distribution.

By inserting the two files into your environment, your visualization will correctly show the different CCTs with the different distributions, a cold white light emitted by the sky and a neutral white light emitted by the sun.

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When inserting sun & sky files separately into your model, make sure you give them exactly the same position in three dimensional space. If the objects aren’t exactly at the same location, one might block light output from the other.

All Innerscene A7 photometric files are scaled to the actual light output of the lighting fixture. Altering of the luminous flux is not necessary. It is also not recommended as it will compromise the correct outcome of your simulation.

The Innerscene A7 IES files don’t have a specified CCT as the IES file format doesn’t allow for it.

When using IES files the correct CCT needs to be applied in the rendering/simulation software. Use 4,500K for the A7-SUN.ies and 3,000 to 12,000K for the A7-SKY.ies

The Innerscene A7 LDT files have their respective CCT saved in the file format. However, most light modeling packages also allow you to change the CCT as needed.

High CCT notes

A normal blue sky is typically 9000K-12000K and we recommend using a high CCT for midday simulations. If too much high CCT light is present in a room, the appearance of the room could appear too blue especially if located adjacent to another space where a lower CCT is present.

By adding additional low CCT lighting to a space where A7 is installed, you will be able to raise the CCT of A7 while achieving an overall balanced appearance.

When modeling Innerscene Virtual Sun Model A7 in your environment, keep in mind the CCT for the sky is adjustable between 3000K and 15000K. Above 10000k the CRI may drop slightly below 90 but remains above 80. If you plan to target a CCT over 10000K and high CRI is also needed, we suggest supplementing the room with additional high CRI/low CCT lighting.

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