What is AR?
AR stands for "Augmented Reality". It is a technique whereby a view of the real world, typically through a mobile device camera, is augmented with additional virtual information.
If you read just one part of this article, make sure it is the section on calibration below: if you don't calibrate your device, chances are you'll get poor results from AR. This applies to all real world AR apps that rely on magnetic compass directions.
How is AR used in TPE?
TPE overlays information about the sun, moon, Milky Way and stars onto your device's camera feed. You can use this to see how the sun etc. will appear at your current location but at different time in past or future.
For example, you could find our when the moon will appear above a landmark in the future, as shown below:
The basic steps to use AR are as follows:
- Select the AR page within TPE (not seeing it?)
- Calibrate the compass alignment (see below)
- Adjust the selected date and time using the date controls (top) or chart (bottom)
- Move your device to view the path or position of the sun, moon, or galactic centre, or to see where major stars and asterisms (e.g. the Big Dipper/Plough) will appear
For example, you might use the AR function to visualize how the full moon will rise across a city skyline.
Important: the indicated sun, moon and Milky Way positions are based on your device's current location.
Here is an overview of the key UI controls and features:
When to use AR
Use AR when you are physically at your planned shooting location. You might wish to check where the sun or moon will rise and track a few hours before your shoot. Alternatively, you might like to see how the Milky Way will be positioned relative to a mountain peak in a few months time.
You can use AR to visualize a shot that includes the sun, moon, Milky Way or stars for your current location but at a time of your choosing. You can use the Az/Alt indicators or the Color Temperature Light Ball to understand the direction of natural light at your location.
Modern mobile devices are incredibly capable things, but for AR applications such as this, the compass is the weak link. Without careful calibration or in the presence of other metal objects, the compass may be adrift by many tens of degrees. Given that the sun and moon are only half a degree across, this can pose a major problem for AR accuracy.
Careful calibration can usually overcome this problem:
- Stay well away from metal objects (e.g. more than 10 feet from cars) - make sure the 'abnormal magnetic field' indicator (a magnet symbol) is not displayed. Move your device away from other objects if it is.
- Make it a habit to recalibrate your device's compass by moving it in a figure-of-eight pattern for at least 10-15 seconds and then choose "reset tracking". Recalibrate and reset when required (i.e. when the calibration "figure-of-eight" graphic is shown).
- Double check the indicated alignment either by checking a well-known compass direction (e.g. does indicated north point in the expected direction?) or by enabling live time tracking and checking that the sun, moon or other visible celestial object lines up as expected.
- Manually adjust the compass offset if necessary to achieve the best accuracy.
If the indicated alignment is imperfect, pan left or right to manually fine tune it: