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Tracking The Sun In New York City
By Lex du Pont

Filming day exterior effectively in New York city demands exacting knowledge of sun position. Through trial and error I have devised a successful way to quickly and precisely track the sun, permitting faster shooting with greater confidence. For the reader to master the technique outlined in this article, I will assume s/he possesses and is experienced using three necessary tools: a precision clinometer to plot the vertical angle of the sun, a protractor to measure the azimuth (the horizontal angle of the sun) on a local map, and a working understanding of the use of fellow guild member David Parrish's excellent computer program sunPATH™. If not, read another article.

Don't bother with a magnetic compass in Manhattan; there are too many magnetic deviations generated by underground pipes and cables, cars, manhole covers and structural steel. A wrong magnetic reading is worse than no reading because it offers false security.

For accurate results, use only true north compass headings. I plot true north headings by using a local map of NYC. (Make sure it is aligned with true north; most maps of NYC are not!) Determine the true compass headings of the location streets with a protractor BEFORE scouting or filming. Use a good protractor because you want your headings to be as accurate as possible. Remember, a couple of degrees makes a difference! Next, use a piece of clear acetate on which to draw the azimuth -- the horizontal direction of the sun -- for any given hour. (Diagram 1).

Use true north as your basis for orientation. Again, accuracy matters! At the bottom of the acetate note the vertical angles of the sun at the corresponding hours. These calculations are from the program SUNPATH™ (set to calculate data for TRUE NORTH). I use a computer drawing program for the hour lines so the subsequent calculations are within a degree. The drawing computer programs, Adobe Illustrator and Claris Draw, I found to be a little tricky because, while true north on a map is found at "straight up" or 0 degrees, in Illustrator or Draw it is found where one would set a line for 90 degrees. Use care in making the adjusting calculations.

Armed with the acetate of the sun's azimuth and vertical angle figures, a map and a clinometer, one is ready to scout locations. Camera positions can be chosen with a rough knowledge of sun position -- rough, because a lot can change between the time of the scout and the shoot day. Moreover, the exact positions of the actors may be move to a different storefront, or an illegally parked car may be blocking the desired camera placement. It is unwise at this time to commit to exact sun positioning.

The shoot day arrives; the placement of the actors is nailed down. Already I have a rough idea of the tracking of the sun, but now I can predict exactly (within 5–10 minutes) what the sun will do on the location. I need only three things: the acetate which shows the horizontal sun position with the vertical angles written at the bottom, knowledge of the true compass heading of the streets, and the clinometer. I stand at the center of the location and align the acetate to true north. If the sun can be seen it is simply a matter of pointing the acetate's correct time at the sun. (Diagram 2)

If it is 8 a.m. I point the 8 on the acetate at the sun. I can predict where the sun will be at any time of the day in relation to that spot by simply sighting the number on the acetate representing the time of day. If I don't see the sun, I align the acetate number corresponding with the time the sun will be aligned with the street. (Diagram 3)

If the sun goes down the street at 10:00 a.m. I point the acetate to the number 10. Then I look at the numbers at the bottom of the acetate and determine the vertical arc by using the clinometer. I see that the sun at 10.a.m. is 45 degrees in altitude, at 11 a.m. it is 55 degrees, at 12 noon it is 63 degrees, etc. That's it.

What makes this method of sun tracking so useful is that it is quick and positive. For example you can be certain that a particular building will block the sun until 10 a.m. After that you're in the sun. The company's goal is defined - get the scene or at least the wide master by 10 a.m. in the shade, or prepare to deal with the consequences. Planning the day takes on a new level of precision due to the speed and certainty of your calculations. You can quickly answer questions such as will the low building across the street put you in the sun and if so, for how long. On one occasion I saved the company at least 2 meal penalties by accurately predicting the sun would not be blocked by buildings after we returned from lunch.

The more you use this system for locating the sun, the more indispensable it becomes. A warning: Do the sun tracking check from both edges of the location. If a building is only 50 feet away, an exact calculation for one place and another spot 10 feet away may be 15 minutes of sun time. Thus your prediction of sun position may be correct for where you are standing, but incorrect for the complete blocking area.

Why do I recommend acetate for the horizontal sun indicator? You may have noticed that I made a grid. The grid represents north south east and west. I can drop the acetate on a map that is true north and place the location spot and align it to true north. It is a quick way to precisely tell where the sun will be on any day at any time.

Remember the learning curve! Try the technique you have just read about a few times before actually using it in a working situation.