Drone camera settings
The problem
Arboair's platform is an image analysis platform that analyzes images to create forest maps which provides valuable information about a forest area. For the analysis method to work optimally and the end product should be as sharp and detailed as possible, there is a range environmental factors and camera settings to take into account at the time of image acquisition. Without without the right knowledge, it can be difficult to make the right decision regarding when it is best to fly and which ones camera settings that will work best with the prevailing environmental factors.
In this documentation we will find out:
- Which environmental factors have an impact on image quality.
- What camera settings we need to understand.
- Which camera settings usually give the best results.
- Which settings we need to take into account in our flight mission planner.
Environmental factors that affect the image
A very large contributing factor to image quality depends on the time of day we choose to fly to collect the images and the environmental factors that are present at the time of the flight. If we don't give ourselves the right conditions from the outset, there are no magic camera settings that can work wonders. Having said that, let's look at some factors that we need to consider when choosing an opportunity to fly.
Sunny/cloudy
When the weather is nice and the sun is shining, it gives a very hard light which will result in what is struck by the sun's rays being very bright and what is in shadow will be very dark in relation. We thus get a strong contrast between light and dark. This harsh contrast results in the very darkest and the very lightest parts of the image usually being completely devoid of information.
When, on the other hand, the sun is behind an even cloud cover, the light over the forest is much more even and therefore the contrast is lower. This means that the image will preserve more information all the way from the darkest parts to the lightest parts of the image, which in turn provides more information in the image and better conditions for image analysis.
Time of day
The time of day will also affect how strong the contrast over the forest will be. Early in the morning when the sun is low and the light hits straight from the side into the forest, the trees will shade each other. This will result in the tops of the trees that are hit by the sun's rays will be very bright and further down on the trees where the sun's rays do not reach, it will be very dark in relation.
When we instead choose to fly in the middle of the day when the sun is at its highest, a larger area of the trees will be hit by the sun's rays, which means that the trees get a more even light and less contrast, which provides better conditions.
Light level
The total amount of light above the forest is also a decisive factor. When we fly in the winter, when there is generally very little light, we need to adjust the camera's settings, which in turn will affect, among other things, how fast we can fly without the images becoming blurry due to motion blur, also known as 'motion blur'
When, on the other hand, we fly in the summer when it is generally more light and we can adjust the camera settings accordingly, we generally have better conditions that allow higher flight speed and provide better conditions for getting consistently sharp images.
Camera settings that affect the image
Now that we know which environmental factors affect the conditions for image quality at the time of collection, we can move on and take a closer look at which camera settings are available and how they affect the image.
Shutter
Affects how long the camera's sensor is exposed to register the image. If the shutter is set to 1/25 second it takes 0.04 seconds for the camera to register the image and if the shutter is set to 1/500 second it takes 0.002 seconds for the camera to register the image.
Since the drone usually keeps a cruising speed when the picture is taken, it is important that the shutter is set relatively high so that the picture is sharp. If the shutter is set too low in relation to the drone's cruising speed, a phenomenon known as 'motion blur' occurs
In the images below, the drone travels at the same speed. In the left image, the shutter has been far too low which has introduced 'motion blur'. In the right image, the shutter speed has been adjusted to the drone's cruising speed and therefore becomes sharp even though the drone is moving:
ISO
Determines how sensitive the camera's sensor is to the light hitting it. When, for example, we have a very high shutter speed, very little light has time to register on the sensor and the image can therefore become dark. By then increasing the ISO value, we can compensate for the fast shutter so that the image gets the right light. The ISO value and the shutter thus affect each other.
Too high an ISO value results in a grainy image with a lower sharpness/detail level. It also provides a lower dynamic range, i.e. the sensor's span between the lightest and darkest things it can capture in an image is smaller.
This is why it is beneficial to fly on a bright day because it allows you to fly with a high shutter speed and a low ISO value.
In the image on the left, the ISO value is set very high and we therefore see that the image is grainier/perceived a little more blurred and that the trees do not appear as clearly because the dark parts are almost completely black due to the lower dynamic range. The image on the right is perceived as sharper and the trees appear clearer with more information in both the dark and the light parts as a result of the positive effects of a lower ISO value:
White balance
Affects the color tone of the image on a scale between warm and cool. A lower 'K' value gives a colder light and a higher 'K' value gives a warmer light.
5600K gives the most neutral colors because that's what our eyes see. When the camera is set to 5600K, the images will always look similar to what we saw with our own eyes when we were out collecting the images.
In the image on the left, the white balance is set very low and the image looks unnaturally cold. In the middle image, the white balance is set to 5600K and looks very neutral as we expect the forest to look. In the image on the right, the white balance is set very high and the image looks unnaturally warm:
Focus
Affects the camera's optical elements to focus at different distances.
In the left image, the focus of the camera has been set too close to the camera and the trees are therefore out of focus and therefore out of focus. In the right picture, the focus has been adjusted to the distance of the trees from the drone and they therefore end up in the camera's focusing range and become sharp:
EV compensation
To make things easier, we can let the camera automatically select many settings and instead use only the 'EV' value to influence how dark or light the image should be. Depending on whether we set the 'EV' value to -1, 0 or +1, the camera will automatically adjust the settings to make the image a little dark, neutral or a little bright.
In general, we want to stay at 0 to get the best results in most scenario. There are scenarios where we need to change the EV. Check out our
Reference image guide to get the best result and to get an even more comprehensive guide when there is winter conditions checkout our
complementary guide for exposure.
In the image example below, we see how the camera adjusts the settings to make the image darker or brighter depending on which 'EV' value we have set:
Picture profile
Affects the appearance and character of the image. There are several pre-programmed image profiles we can choose from, but there is also a 'custom' profile where we can choose how the image should be registered.
What we are interested in influencing is the contrast of the image. By choosing everything between -3 to 0 to +3, we influence how little or how much contrast there should be in the image.
As a rule of thumb, we want to lower the contrast as much as possible to capture as much information as possible in the image.
In the image example, we see how the contrast is affected depending on the contrast level we have chosen for the image profile.
