Multispectral cameras are commonly used to track changes in plants because they can usually measure at a higher resolution and cover more area than traditional hand-held solutions.

A plant will reflect the ambient light differently depending on the plant's particular life cycle stage and health. As a plant grows the leaves may start out more red and then turn green. Flowers may develop. If the plant is subjected to pests, poor soil or less water it will also change the color of the plant. These changes can be captured with a properly selected multispectral camera.

It is very common for researchers to read previously published papers to gather information about methods and results achieved from previous experiments. MAPIR has supplied the research community for over 10 years with a variety of equipment and supporting software, which you can review at the link below:

Multispectral Camera Applications for Plant Research

Changes in Plant Health

Probably the most common application for using multispectral cameras is to assess the health of plants. A plant's health is commonly measured by computing the relationship between the amount of near infrared (NIR) and red light that a plant reflects. A healthy plant will reflect more NIR light and less red light than a plant that is dying, as you can see in the graph below. The NDVI formula is commonly used to assign a value to plant health, with a higher value (0.8) being a healthy plant and lower values (0.3) being dead. 

A plant's health can be affected by many situations, such as an infestation of pests, poor soil or lack of water. Researchers will often subject the same type of plants to various adjustments to see what effect there is, which the multispectral camera can track over time.

Changes in Plant Growth

Besides the general health of plants a researcher may want to track changes in how the plant grows. Plants subjected to additional nutrients may grow more quickly than those that are not, so the shape is an important metric to also track. It is important to use a background behind your plants that will not affect the multispectral indices you plan to use, so that masking the plant data from the background is more easily accomplished. An inexpensive material that we recommend using is white cotton, such as clothing or bed sheets. White cotton usually produces NDVI values near 0, which is easily masked out, as you can see in the leaf animation above.

Multispectral Camera Solution from MAPIR

Using MAPIR's Solution for Plant Research

MAPIR offers everything you need to fully measure how light is reflecting off of the plants. The ambient light sensor records the light spectrum shape, the multispectral cameras record the intensity of the reflected light per pixel, and the reference targets correlate image pixel values to percent reflectance.

Calibrating for Mixed Ambient Lighting

It is very important when performing multispectral imaging that you measure the ambient light spectrum. This is because the scene often times has mixed lighting, such as sunlight and an artificial light source. The ambient light may also change over time of day or day to day. To accurately measure the ambient light spectrum you can use our DAQ-A-SD light sensor.

Calibrating Reflectance Data Over Time to Track Changes

If you are measuring plant changes over time then it is very important that the data is calibrated to the same reference standard each time. MAPIR offers our T3 calibration targets to perform this standard reflectance calibration. Simply capture an image of the target while the light sensor is recording the ambient light spectrum and the final processed images will be comparable even when the ambient light changes.

Common Camera Filter Selections for Plant Health Research

As mentioned above one of the most common traits that are tracked is plant health. Plant health assessments commonly compare the near infrared (NIR) and red light reflectance. You can also use orange light alongside or in place of red light. Blue/cyan light is also useful if the plant is more of a blue-green, or if the plant is in/under water.

Usually the best filter option to choose for plant health is our RGN (red, green, NIR). It will capture both the NIR and red light necessary for NDVI, etc, as well as capture green light, also common in many vegetative indices. If you are purchasing another camera we suggest the OCN (orange, cyan, NIR) filter model. Combining the RGN and OCN allows you to capture 6 different spectrums of light, which you can see illustrated on the graph below.