Flash module calculates the distance for which the flash provides optimal illumination. The distance is calculated diving the guide number (GN) by the aperture.

The guide number is adjusted based on the flash head zoom position, flash output power, and camera ISO sensitivity.

ISO values are limited to the ones that the selected camera supports and aperture values are limited to those of the selected lens.

Underexposure and overexposure warnings are displayed when the distance is too close or too far from the camera for the current combination of settings.

To correct underexposure one or more of the following adjustments should be made:

  • Decrease the distance
  • Open up the lens by selecting a larger aperture (smaller value)
  • Increase the guide number by:
    • Selecting a longer zoom head position
    • Increasing flash output power
    • Increasing ISO sensitivity

To correct overexposure one or more of the following adjustments should be made:

  • Increase the distance
  • Stop down the lens by selecting a smaller aperture (bigger value)
  • Decrease the guide number by:
    • Selecting a smaller zoom head position
    • Decreasing flash output power
    • Decreasing ISO sensitivity

The selected camera and lens are displayed at the bottom of the screen and can be changed by clicking the disclosure button next to them.

When imperial units are selected, you don’t need to use the foot and inch signs. Just enter the feet and inches values separated by a space.