Compared to the Phantom 1 days, we drone operators now have so many tools to work with! Serious aerial photographers are especially excited to have two small drones now that allow complete control over the three variables of the exposure triangle. Both of these drone cameras also have a relatively large 1” camera sensor. These drones are the DJI Mavic 2 Pro, and the DJI Phantom 4 Pro. Despite the drones being listed as consumer-level, a photographer with experience can certainly use either of these quad-copters for high-level professional-level work
Not many people are aware that there is a wonderful little tool incorporated in the Mavic 2 Pro and Phantom 4 Pro drones. The tool is hidden in the DJIGo4 app. It is called the spot exposure meter.
Tucked away under the green auto-focus continuous indicator icon, on the second row of camera info icons, is the spot meter tool. Tap on the green box to reveal the yellow circle. This is your spot meter. Now tap anywhere on your viewing device. Watch the exposure change, depending on where you place the yellow circle. A spot meter reads the brightness of a particular spot within your camera’s frame. The field of view for your spot meter is approximately 5º. Regardless of the exact field of view, this function allows us to work quickly; jumping between tap-focus, and tap-exposure as necessary. This tool also allows us to select the spot for which the camera will set its exposure. Keep a couple of things in mind when trying this valuable tool:
- The spot meter only functions in when your camera mode is set to Automatic (A).
- If you tap on the tiny “+” on the edge of the yellow circle, the camera’s meter will default back into center-weighted averaging.
Why is this spot-meter so valuable?
1) We can expose for the subject, by quickly overriding the default center-weighted average metering.
2) We can create a manually bracketed set of exposures to process later as an HDR (High Dynamic Range) image.
Let’s expand on these scenarios:
Exposing for the subject
Exposing for the subject can be tricky when your camera’s light metering system is trying to average the entire scene. A high-key scenario (or overall bright scene) will result in a backlit subject. The subject, being a small part of the overall image, will appear very dark, being underexposed.
In other situations, you may want to place your subject towards the edge of the frame rather than in the center. The center-weighted metering system will give less regard the light values near the edge of the frame, leaving your subject improperly exposed. Using the spot-meter, you can tap on the subject directly for accurate exposure.
Create a manually bracketed set of exposures for an HDR image
An HDR photo is created by merging a bracket set of exposures into a single image. The process requires tone-mapping software. Adobe Lightroom, or Skylum Aurora, or HDRSoft Photomatix are all capable. This technique helps the photographer manage unruly lighting situations – situations where the range of light is too broad for the camera’s sensor to capture.
What you see with your eyes is not the same thing that your camera will capture. Your eyes can detect a range of approximately 24 values of light from pure white to pure black. Our small drones generally capture and record one-third of this 24 E.V. dynamic range of light. Bracketing a series of exposures and merging to HDR is the standard workaround.
When would you use HDR? When there are extreme highlights and deep shadows in the same scene. Shooting into shadow areas in the middle of a bright sunny day would be a typical situation where a photographer might incorporate HDR techniques.
The DJIGo4 app offers us auto-exposure bracketing (AEB) mode. Kudos to the engineers for that. However, the AEB range is not broad enough to create a satisfactory HDR image. We are given a choice of 3 or 5 bracketed shots (captured in rapid sequence while the drone hovers). The separation between exposures is not wide enough to cover the range of light typically needed to cover most HDR scenarios. The DJIGo4 app gives us a bracket of -0.7, 0, +0.7 exposure values. Or when bracketing five exposures, -1.4, -0.7, 0, +0.7, +1.4 EV’s. Honestly we really need a range of -3.0, -1.5, 0, +1.5, +3.0.
Well, taaa-daaah! Using the spot meter tool can get you to that wider bracketing range!
Our drones are so stable in the air now that they rival a tripod. This stability gives us the confidence to create a manually bracketed set of exposures, which takes a few seconds longer. We are no longer afraid that the drone will drift, resulting in misaligned images.
So, when hovering over a harsh lighting situation:
- Tap that green square box to open the spot-meter.
- Tap on a highlight area, then capture the photo.
- Tap on a dark area, then capture a second photo.
- Tap on a mid-value area (or the “+” on the edge of the circle), and capture a third photo.
- Merge all of these into an HDR image and it will be epic!
In fact, two photos will work in most instances. The more photos you throw into an HDR, the more noise/artifacts will be introduced into the final image. Keep it simple when you can.
That little green box in the DJIGo4 app is hiding a very useful tool. Get out and try using the spot exposure meter during your next flight. Keep it open when you are trying to work quickly or want to create your next bracketed HDR image.