An introduction to Mechanical Shutters

Drones are revolutionising data collection across a number of sectors, transforming how professionals like those in agriculture, construction, surveying, and environmental monitoring operate. They're not just speeding up the process but also enhancing the quality and safety of the work. What seemed like a sci-fi fantasy just ten years ago — drones swiftly flying and capturing detailed images — is now a reality, thanks to advancements in DJI technology. These devices are now essential for creating comprehensive maps and terrain models.

Today, drones are the preferred choice for mapping and aerial surveys. Typically, a UAV follows a predetermined route, capturing images at set intervals and altitudes. These images are then intricately pieced together using sophisticated software to produce precise maps.

In this piece, we'll explore the technology behind this transformation, focusing on a crucial element that distinguishes high-end mapping drones: the mechanical shutter.

We'll delve into what a mechanical shutter is, how it differs from other shutter types, and its critical role in capturing top-quality aerial photos.

CMOS Sensors

To grasp the significance of mechanical shutters in mapping and surveying, it's helpful to start with the basics of how cameras, including those on camera drones, function.

A camera captures light through an image sensor, which consists of numerous tiny pixels. These pixels are formed from a substance known as a complementary metal oxide semiconductor (CMOS). The CMOS converts incoming light into an electrical charge, which then produces the image.

The role of the shutter is crucial here. It determines the duration for which the CMOS is exposed to light. When the shutter is open, light can enter and strike the CMOS. During image capture, the shutter briefly opens, allowing light to reach the CMOS, resulting in the creation of an image.

How mechanical shutters differ from the rest

Various shutter types exist, each exposing the CMOS sensor's pixels to light differently.

Focusing on the mechanical shutter, preferred by mapping experts and used in devices like the Mavic 3 Enterprise, Phantom 4 RTK, and Zenmuse P1 sensor, we see a distinct method of operation. Mechanical shutters expose the entire image sensor to light simultaneously, ensuring that each pixel captures the same moment in time. This synchronicity is crucial, especially when compared to electronic or rolling shutters.

In contrast, electronic shutters illuminate the image sensor pixel by pixel, line by line, from top to bottom. This sequential exposure results in a slight delay between the exposure of the top and bottom of the frame. While generally not problematic, this delay can lead to the rolling or jello effect — a distortion commonly seen in images of moving subjects or when the camera itself moves rapidly, as in drone mapping.

Importance of mechanical shutters for mapping

Professional surveyors' work is often evaluated based on its precision. Nowadays, many drones are equipped with RTK (Real-Time Kinematic) technology, delivering measurements with near-perfect accuracy. This leaves little room for poor-quality images that might compromise the integrity of the results.

Opting for a drone with a mechanical shutter is key to achieving the highest quality images, significantly reducing the chances of encountering the unwanted 'jello effect.' Unlike electronic or rolling shutters, which can cause motion blur, mechanical shutters eliminate this issue.

While camera and subject movement might not be a concern in static scenarios, the dynamic nature of drone photography demands a shutter capable of delivering clear, distortion-free images from a moving viewpoint.

So, why does this matter for aerial surveys?

Accuracy is paramount for professional surveyors. Rolling and electronic shutters, prone to distortion due to their exposure methods, are less suitable for mapping tasks. Even minor jello effects from a rolling shutter can mislead mapping software, affecting the orientation and ultimately the precision of the measurements.

Article Credit: DJI