Complementary drone guide winter

​​In winter conditions, when the ground is covered with snow, collecting images with drones presents a challenge. In such a landscape, the drone camera may inadvertently underexpose the image. To counteract the reflective surface, the exposure should be adjusted above 0.

When flying a drone, it is necessary to observe the screen and monitor the image collection in the system. In a forest area with snow-covered ground, the contrasts between the white ground and the green trees become significant. In snowy conditions, the camera's light meter can be easily fooled by the bright, reflective snow, often resulting in underexposed images where information in the image is lost. Usually the snow is well exposed, while the trees risk being too dark and lacking detail in the shadows. To counteract this problem, you can use exposure compensation to deliberately overexpose your images and capture the true brightness of the snow. As an operator, you can monitor the screen and ensure that the trees are exposed satisfactorily without being too dark. In-flight exposure can be adjusted as needed to ensure accurate image acquisition in snowy conditions.

Here's a more detailed explanation of how to use exposure compensation in snowy conditions.

Understand exposure compensation

Exposure compensation is measured in exposure value (EV). Each step represents doubling or halving the amount of light captured by the camera. Positive exposure compensation values ​​(+1, +2, etc.) let more light into the camera, resulting in a brighter image, while negative values ​​(-1, -2, etc.) reduce the amount of light and create a darker image.

Adjust exposure compensation

In snowy conditions, you usually want to use positive exposure compensation to brighten your images. Start by setting your exposure compensation to +1 or +2. Remember that the optimal exposure compensation can vary depending on the specific lighting conditions, so you may need to experiment to find the best setting for your situation.

Monitor the histogram and overexposure warning

When adjusting exposure compensation, you should keep an eye on the histogram and overexposure warning (zebra stripes) on your DJI drone's screen. The histogram shows the distribution of tones in your image, while the overexposure warning highlights areas that are too bright and will lose detail. Use these tools to fine-tune your exposure compensation settings and ensure you achieve a well-exposed image without blowing out highlights.

Example

The histogram is read from left to right where the left side represents the darkest parts of the image and the right side represents the lightest parts of the image. When the histogram output 'hits' one of the ends marked by the red lines, it means that some parts of the image have fallen outside the 'dynamic range' of the image and lack information. In this example we can see on the histogram that we have all the information in the dark parts because the rash ends before the red line on the right side however we can see that the brightest parts of the image are overexposed indicated by the rash taking in the red the line on the right side and there will be missing information.

The zebra pattern shows where the image is overexposed. In this example, we can see exactly where the image is overexposed and missing information. Best we lower the exposure compensation until the zebra pattern disappears from the trees so we know we're keeping the information in the trees.

Balance highlights and shadows

When using exposure compensation in snowy conditions, it is important to strike a balance between brightening the image enough to capture the true brightness of the snow and maintaining detail in both highlights and shadows. Since snow conditions can vary greatly, it's crucial to experiment with different exposure compensation settings to find the ideal exposure for each situation. Review your images on the drone's screen or a connected device and make adjustments as needed to achieve the desired exposure. With practice, you will become more adept at judging the optimal exposure compensation settings for different snow conditions.

Tip

In cold winter conditions, it is recommended to allow the drone to acclimatize to the ambient temperature while keeping the batteries warm. This prevents snow particles from swirling onto the drone and melting, which later in flight can result in an icy coating on the drone's surface. However, batteries should be kept warm to ensure proper operation, either in a heated vehicle or close to the body to avoid freezing.