LightTools Enewsletter

December 2016

Thank you and Happy Holidays

LightTools Tech Support During the Holidays

From December 26, 2016 to January 2, 2017, please allow for a delayed response to your request for LightTools technical support. Our technical support will be very limited during this time and will only be available by e-mail. 

We will resume business as usual on January 3, 2017, and will respond to product support and general inquiries. You can contact us via e-mail at

Thank you for your patience and understanding.

In countries where we have international representatives, you can contact the distributors directly. Please see our list of global contacts on our website.

In the meantime, our Customer Support Portal ( is available at any time. As a current customer, you have access to training materials, user group presentations, sample system and application files, FAQs, macro downloads, recordings of previously held webinars, and more.

Customer Support Portal

If you haven’t already registered for Portal access, consider registering for an account today!

*Please note that for current customers signing up for an account, it may take 1-2 business days for us to activate your account.  Please note that for December 24, 2016 through January 3, 2017, there will be a delayed response.  Your account may not be activated until after January 3, 2017. 

Customers can check out the following videos and updates:

LightTools Quick Tip: What Photometer Type Do I Need?

LightTools has three receiver orientations you can choose from to visualize angular illumination data (i.e., intensity, angular luminance, etc.). These orientations are equivalent to the IES standard photometry types A, B, and C. Each orientation uses the same ray data, but presents it on a different grid. The particular photometry type and orientation that is most appropriate for you will depend on your application. If you have a rotationally symmetric system for example, type A or B will be better suited for a narrow beam distribution with the peak along the optic axis. For a distribution like a batwing beam pattern (or a donut-shape), Type C photometry will work better.

You can choose a receiver’s photometry type in the Orientation tab:

Orientation Tab

In addition to the photometry type, you can choose the orientation of the receiver using Data Vectors (i.e., the 0,0, or Nadir, direction) or Angular coordinates (i.e., Euler angle):

orientation of the receiver

The default photometry type for far field receivers is Type C photometry, with the Nadir pointing along the global +Z-axis. For surface receivers, the default is Type B photometry with the 0,0 pointing along the surface’s +Z-axis.

Type C Photometry

In Type C photometry, the coordinates used are latitude and longitude (V and L, respectively). Latitude values start at one pole (0 degrees V), scan toward the equator (90 degrees V), and continue increasing to the opposite pole (180 degrees V). The longitude scans around the equator and sweeps from 0 degrees L to 360 degrees L. Note that when angular meshes are displayed, the 3D window shows reference coordinate points to help you conceptualize the orientation with respect to your model.

Type C Photometry

Type A Photometry

In Type A photometry, the coordinates are measured in horizontal and vertical angles (X and Y, respectively). The 0,0 point is now aligned with the equator where bins are roughly rectangular. The poles in Type A photometry are aligned with the Y direction. The X scale goes from -180 degrees to 180 degrees, and the Y scale goes from -90 degrees to 90 degrees.

Type A Photometry

Type B Photometry

Similar to Type A photometry, Type B photometry is measured in horizontal and vertical angles (now H and V, respectively), with the 0,0 point aligned along the equator. Types A and B photometry differ in the poles. In Type B photometry, the poles are aligned along the horizontal direction. The H scale goes from -90 degrees to 90 degrees, and the V scale goes from -180 degrees to 180 degrees.

Type B Photometry

Below is an elliptical intensity pattern created by using a collimated source incident on an elliptical Gaussian scatterer.

elliptical intensity pattern

The far field intensity for each photometry type can be compared by changing the receiver orientation:

Click the image to open a larger version in another window

Even though the data is the same, the intensity mappings can be quite different depending on the orientation, particularly between Type A/B and Type C.

Receiver Binning Implications

When measuring the angular illumination distribution (intensity, angular luminance, etc.), the measurement grid is mapped to a globe. Near the equator the angular receiver bins form rectangular cross-sections on the globe, and bins adjacent to the poles have triangular cross-sections. In addition, the solid angle of a bin at the equator is larger than the solid angle of a triangular bin near the poles. There are implications that since the bins near the receiver poles have a smaller solid angle, they may collect few rays, resulting in measurements that are inherently noisy.

For Type C photometry, the mesh Nadir is centered around the pole. The following figure shows a low resolution Type C mesh, where you can see the triangular bins near the mesh center.

low resolution Type C mesh

The solid angle of each bin for each photometry type shows where data is likely to be noisiest. In the following figure, the CellSurfaceArea for the mesh is plotted for each photometry type.

Click the image to open a larger version in another window

This representation guides us towards the distribution patterns that are more suited to different photometries. For instance, the bin areas are identical along the horizontal direction for Type A photometry. As such, it is most appropriate to use Type A photometry in applications that measure intensity over the horizon (such as an automobile headlight).

Polar vs. Cartesian Mapping

For Types A and B photometry, you might see differences for non-symmetric distributions. Note how the data appears the same for Type A and Type B when both are represented using a Polar mapping, but the pattern appears different with Cartesian mapping.

  Polar Cartesian
Type A
Type B


LightTools provides numerous ways to visualize angular illumination data by providing receiver orientations based on industry standards. We hope this helps you understand the options and controls LightTools provides in order to analyze your system and visualize the data.

Student Optical Design Competition Winners

Every year, students are invited to participate in the Robert S. Hilbert Memorial Optical Design Competition. Students can enter an optical design class assignment or thesis work that uses CODE V or LightTools. We are pleased to announce our 2016 winners:

  • Francisco Santos
    University of Rochester

  • Matt Kozun
    University of Saskatchewan 

  • Furkan Sahin
    University of Southern California 

  • Weichuan Gao 
    University of Arizona
student competition

To see their winning entries, please visit our website.

For competition rules, frequently asked questions, and entry form, see our website. Entries for the 2016-2017 year will be accepted until June 15, 2017.

Congratulations to our winners!

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