One way to take root picture using a camera is to put the root system on a flat surface and take picture from above. This technique is fast and can be used with large root system.
Here is a couple of things to think of before taking such image.
This technique can be used with large root system as it is possible to separate the different root on the chosen surface. It is important to carefully spread the root in order to avoid overlaps and crossing as much as possible. They are a nightmare for most of the root image analysis softwares.An easy way to separate the different root is to place the root system in a thin film of water. The roots will tend to recover their initial shape and they are easier to untangle as they float. Be careful that using the camera flash on water will create many reflexion. It is recommended to either remove the water once the roots are spread of the use indirect light (e.g. a spotlight directed a the ceiling).
Choose a camera with a high-resolution. If the resolution if too low, the number of pixels contained in the roots will be too low to extract any information. In order to increase the resolution, it is also possible to take the picture closer to the roots, but his will need an adequate lens.<h3>About the background</h3>Choose a background with a color different from the root (usually black is working well). Also be careful not the choose a “shiny” background, as it can create noise in the last image which can impedes the later analysis.
When you take a picture with a camera, its scale (pixels/cm) will change if the distance between the object and the camera changes. It is therefore important that an object of a known size is present in the picture to scale your image during the image processing steps.