AMITIAE - Saturday 14 April 2012

Tracking the Sun and the Moon: LightTrac - an iOS App for Photographers

apple and chopsticks


By Graham K. Rogers


The most important ingredient in any photograph, apart from the subject itself, is light. While photographers in the studio have access to artificial sources, those who work outside rely on natural light. It is quite important when setting up a shoot to know where the sun (and to a lesser extent the moon) will be. There is, of course, an app for it.

I recently read and reviewed Jeff Carlson's useful book, The iPad for Photographers: Master the Newest Tool in Your Camera Bag which outlines several ways in which users might leave their bulky computers at home and work on the road with the lighter tablet device.

As part of the ideas he outlines, there are several apps introduced. While I found that I already had a number of these, mention of LightTrac had me scurrying to the iTunes App Store, where I downloaded the ($4.99) app for tracking the paths of the sun and the moon.

The app installed on the iPhone as well as the iPad. Although the larger screen of the tablet device does make it easier to work with, it is quite usable on the iPhone. With the different displays, LightTrac works almost like two apps. As a note, the icon for the app is beautifully made, which always signals to me a certain pride that the developers have in their work.

LightTrac - iPad

Unlike the iPhone (below), all of the controls are accessible from the main panel when in landscape mode, while there is also a graphic of the sun and moon rising and setting when in portrait mode. This can be scrolled sideways to reveal two more screens: an elevation chart and azimuth chart; and a shadow length indicator (see below - iPhone).

Controls are above the main part of the display: a map or satellite image of a selected (or current) location. There are three lines over the display: red, yellow and blue. Red shows the current position of the Sun or Moon (depending on which has been selected). Yellow shows Sun- or Moon-rise, Blue indicates Sun- or Moon set. There are buttons for Date, Location, Save this Spot, Sun/Moon and Map/Satellite.

iPad Display: Landscape Mode

Below the Map/Satellite display is data about what is displayed and a slider which adjusts the time from the current: backwards or forwards. As the slider is moved, so the red line is repositioned -- of great value when deciding on how to shoot -- while data displays (elevation, time and angle) are also changed. A date icon allows the user to select a month and day using scroll wheels. A single arrow reset icon (twin-arrows on the iPhone) returns the settings to the current time and date.

The Location button shows a list of pre-selected locations. A search panel uses the Google map selected. A bookmarks icon accesses Address Book data, and clicking on any address shown, brings that up on the main display.

Unfortunately, not all locations have addresses and while the app is set up for the US, working in other countries may show some shortcomings with the Google search facility and the map display. As I had previously toured extensively by motorcycle in some remote parts of Thailand, I tried to find these locations. There were some errors and one search gave me a map display several kilometers away from the true location which was actually marked on the map.

With some local knowledge, playing about with the map size and swapping between satellite and map, I was able to come up with the areas I was interested in. On the iPad, using the Save this Spot button, then enables the user to save the location (with coordinates) for easier future access.

Hills and Forest, Kanchanaburi Province - iPad Display: Portrait Mode

LightTrac - iPhone

LightTrac The smaller screen of the iPhone limits what can be shown, but the developers have done a good job of reorganising the app. The display is in five sections: Light, Shadow, Locations, Search and Help. The icons for these are shown at the bottom of the screen in landscape mode. In portrait mode there are selectors displayed on the maps: Sun or Moon to the left, with Map or Satellite buttons to the right.

At center top in landscape mode is an "i" icon which reveals data about the current settings (the top panel on the iPad in portrait mode). Below the buttons are Rise and Set times, depending on which is selected (Sun or Moon).

Below the Map/Satellite display (just above the tool icons) is data about what is displayed plus a slider to adjust the time from the current: backwards or forwards. As the slider is moved, so the red line is repositioned, while data displays (elevation, time and angle) are also changed. A date icon allows the user to select a month and day. A twin-arrow reset icon returns the settings to the current time and date.

A Shadow tool uses a 6ft (or 6M) tree to indicate the length of shadows at various times of day at the location selected. For example at my current location, the shadow length is 0.9m, while at 6:20 pm, just before sunset, this will lengthen to 184.2m, while just after sunrise the same 6m tree would cast a 1595m shadow.

LightTrac LightTrac

These changes in light and angles are of much importance when taking photographs. On the iPad this is one of the panels shown above the map data when in portrait mode

Of course, from my apartment window, I know that the sun rises (more or less) between two apartment buildings to my left and sets behind my bedroom window, but I do not take all my photographs in the apartment. Like anyone with a camera, I visit different locations. The Search and Locations icons access tools that help users examine a scene before a visit.

LightTrac LightTrac

Sun and Moon - Satellite and Map

The Location button shows pre-selected locations. A search panel uses the Google satellite maps only on the iPhone with the Search panel at the top. A bookmarks icon accesses Address Book data as on the iPad. While finding a location is similar to the feature on the iPad, there is no Save Location button. Instead, on the map display in portrait mode is a floppy disk icon. On some maps this is not easy to see. In landscape mode, the same icon is shown in the panel to the right of the map with data about the location selected.


With maps and search facilities incorporated, this makes planning a trip -- or more specifically, a photographic shoot -- a little easier. There is nothing like turning up at a beautiful location and finding that the sun is hidden behind a mountain, or that at the time planned for the shoot, the shadow angles are all wrong.

There is a considerable amount of information used to display the various angles of the sun and moon during a day (indeed, during the year). For example, where I am, in June the noonday sun is south-east of here; today it was almost due north. In the Northern and Southern hemispheres, sunrise and sunset occur in widely different directions depending on the month and latitude.

Although this was introduced to me as an app for the iPad, the iPhone installation -- while markedly different in operation and display -- is every bit as usable. It would also make sense to install on both devices as there is a chance that the iPad could be tied up with other photographic functions that it is capable of.

This is a highly useful app for those who need to know the positions of the most important natural light sources -- sun and moon. Not only can users have this critical information for the current location, but features within the app allow a discovery process for areas that might be be visited in the future.


Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs.



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