Footprints™ Tutorial

The Footprints™ interface should be self-explanatory to those already familiar with template generators, but for others the following walk-thru should be helpful.

Template Specification

Hit "Enter" on your keyboard when presented with the above screen, and then browse for "GW4X4M.ies", the photometry for our G18-4XL-400MH. (The larger Gullwing.) You should already have a variety of IES files saved on your PC or network. If not, download some of our photometry. Footprints™, like all other lighting software, must read data from such IES files to run calculations. How else could it know how much light you get from that new luminaire produced by Brand X?

Next, hit "Tab" to get to the next field: Lumens Per Lamp. With most of our files, the default value will be "1000" - likely NOT an accurate value for your lamp. The user is expected to use a realistic value as published by a LAMP manufacturer. For this exercise, let's use "40000".

Tab again to the Light Loss Factor field. This is probably the most complicated input value of all, and because it depends on a multitude of variables including often unknowable site conditions, the lighting industry generally defaults to something like 0.72 for metal halide and 0.80 for HPS. Let's use the former.

Go to the Arrangement field and select your pole assembly. The available options should cover just about every head arrangement you'll need. Let's use "Single" for this exercise.

In the Optical Height field enter the vertical distance from the horizontal calculation plane to the luminous center. The luminous center is taken as the center of the lens for cutoff-type luminaires (i.e. an opaque box with a horizontal aperture in the bottom surface, beyond which nothing protrudes), as the center of the arc-tube for noncutoff-type HID luminaires with a clearly visible lamp, and as the approximate "center of gravity" of acorn-type luminaires. For this exercise, let's use "32", representing a 30' pole on a 30" concrete base, less the depth of the housing.

For Arm Length input the horizontal distance from the center of the pole to the optical center. Let's use "1.5" to approximate the Gullwing.

The Tilt should be left at zero for everything but floodlights. The deliberate tilting of a Gullwing is universally regarded as the most despicable of sins... We don't recommend tilting any of our cutoff luminaires. (You might as well buy a floodlight!)

For the time being let's skip over the Description field and the Include check box.

Tab to the Scale field. If you're working with a scaled plot, you should probably enter the scale of the drawing. (For example, enter "20" if your scale is 1"=20'.) Otherwise, scale just determines how large the template appears on-screen. If you used "1000" your template would probably be a tiny dot on the screen, and if you used "1" nothing would appear - the template is so large all of the curves fall outside the window, maybe even beyond your monitor! As a rule, use a standard value equal to or slightly greater than your optical height, so let's use "30" for this exercise.

Next is the Isoline Preference field. The default value is "Factors of 2". This means curves will be shown at the Target Min (minimum) value, 1/2 the minimum, and maybe 1/4 the minimum. (The Target Min is specified two steps from now.)

When generating a template, laymen are often tempted to follow the "more is better" mantra: They show a dozen curves (isolines) at every value but the one they are designing to... You really only need (and want) 2 isolines in most cases, occasionally 3. Any more merely add visual clutter. "2" is the default, and with good reason, but let's use "3" for Number of Isolines to dress-up this exercise a little.

Finally, let's specify the minimum horizontal illuminance (footcandle) criterion in the Target Min field. Note that nowhere in that last sentence did we mention "average". Templates are useless when designing to an average illuminance level - they only work for minimum criteria. Let's enter a value of "1" for this exercise.

Tab over to the Calculate button and hit "Enter" on your keyboard. In a moment the following should appear:

You're looking at THE characteristic template for the particular combination of input values you entered. If you change any of these parameters for your project, you MUST run another template. The contents of this screen should be self-explanatory, but note that we report the Maximum Illuminance. Many template generators don't provide this info on-screen, though it is very useful in predicting uniformity.

By clicking the button with the printer icon you will send a black-and-white, 8.5" by 11" page to your default printer. If your current default printer is a good one for the job, go ahead and give it a try. Otherwise, go to Start-Settings-Printers, right-click on the desired printer, and choose "Set as Default Printer".

If you have CAD-type software that can open DXF-format drawing files, try the DXF button and save to some place you'll remember, then take a look at it with your CAD software. This somewhat unusual feature allows CAD users to bring templates into their electronic drawings, allowing them to design without any other lighting software.

Let's return to Template Specification by clicking on the Close button. (Or hit "Enter" on your keyboard.) One powerful feature of Footprintsâ„¢ is its ability to overlay one template over another, providing a means of on-screen comparison between competing optical systems. Click on the Form 2 (Optional) tab with your mouse, and you will see a new input form in which you can specify a second IES file, etc. Go ahead and grab "ECFH4M.ies", which represents the ECA18-FH-400MH, Emco's Ecolume, and give it 40000 lumens. Change the height to "31.5" to reflect the increased housing depth.

The Description can usually be left as-is. It will help you differentiate templates when comparing optics, and would only need to be changed if you were evaluating the effect of some variable (maybe height) on a single IES file.

The Include box is checked by default as soon as you load the IES file. If you don't want to see a Form's template in Preview, just uncheck this box. Leave it checked for this exercise.

Reduce the isolines to "2" and enter "0.5" for the minimum. This will clean things up for our on-screen comparison. Calculate again and you'll see this screen shortly:

Note the increased maximum and the decreased area of coverage for the Ecolume, offset by a marginal advantage in forward-projection. Remember that Brand X can be compared in precisely the same kind of head-to-head overlay comparison...

Note also that in comparison mode the Print and DXF features are disabled. Such a comparison would be very visually cluttered when printed, and in the end it is simpler for CAD users to export DXF files one-at-a-time.

At this point it would be a good idea to adjust your personal preferences. Close out from your Comparison and go to Tools-Settings to specify the root directory for your IES files:

This should typically be "C:\IES\" which contains your "Gardco Lighting" and "EMCO Lighting", etc, folders. This can speed you up considerably if the root directory is instead somewhere on a network or if it's several steps from the default "C:\" path. You can also change the DXF path, printer alignment, and units here. Go to File-Save to register your changes.

This marks the end of the online tutorial. The FAQ page offers a few more advanced tips.