PDAF vs CDAF: Understanding Autofocus in Embedded OEM Cameras
- Vadzo Imaging
- Dec 12, 2022
- 3 min read
Updated: Oct 23
When selecting an embedded OEM camera for your project, one of the most important considerations is its autofocus technology. Autofocus ensures that the camera automatically adjusts the lens to achieve the sharpest image possible, which is crucial for applications such as self-service kiosks, industrial robots, drones, medical devices, and inspection systems.
The two leading autofocus methods used today are PDAF (Phase Detection Autofocus) and CDAF (Contrast Detection Autofocus). Understanding PDAF vs CDAF is essential because the choice affects speed, accuracy, hardware requirements, and performance in real-world environments.
In this blog, we’ll explore how PDAF and CDAF work in embedded cameras (not DSLRs), compare their advantages, and guide you on which technology suits your application best.
What is PDAF in Embedded OEM Cameras?
Phase Detection Autofocus (PDAF) is a sensor-based autofocus method that uses dedicated pixels on the image sensor to detect phase differences in incoming light. Unlike DSLRs, which relied on separate mirrors and AF modules, embedded cameras implement PDAF directly at the sensor and ISP (Image Signal Processor) level.
How PDAF Works:
Special PDAF pixels on the sensor capture light from opposite sides of the lens.
The ISP calculates the phase difference, determining if the image is front-focused or back-focused.
This calculation provides both the direction and the amount of lens adjustment required.
The lens actuator is then moved instantly to the correct focus point.
Because PDAF can predict focus rather than searching for it, the system achieves focus in milliseconds, making it ideal for real-time applications.
PDAF Advantages:
Extremely fast focus response, even for moving objects.
Works well in dynamic environments such as robotics, AR/VR, and drones.
Low-latency performance supports real-time interaction in kiosks and automation systems.
What is CDAF in Embedded OEM Cameras?
Contrast Detection Autofocus (CDAF) is a software-driven autofocus method that does not require dedicated PDAF pixels. Instead, it analyzes the contrast of the captured image directly from the sensor.
How CDAF Works:
The camera measures edge contrast in the live image.
The lens actuator moves step by step, with the ISP checking whether contrast increases or decreases.
The lens continues moving until the peak contrast is reached, which represents perfect focus.
CDAF is slower compared to PDAF because it relies on trial-and-error adjustments, but it delivers high precision in controlled environments where the subject is static.
CDAF Advantages:
Very accurate for still or slow-moving subjects.
Works on any standard image sensor without hardware modifications.
Cost-effective and reliable for applications like medical imaging, scanning, kiosks, and industrial inspection.
PDAF vs CDAF: Key Differences in Embedded Cameras
Both technologies aim to achieve sharp focus, but their working principles and application suitability differ significantly.
Here’s a comparison of PDAF vs CDAF in embedded OEM cameras:
Hardware:
PDAF requires specialized pixels (phase detection pixels) that are divided into right and left halves on the image sensor. These pixels capture light from opposite sides of the lens to measure phase difference, enabling the camera to calculate lens adjustment quickly.
CDAF does not require such half-blacked pixels. Instead, it uses the existing standard image pixels for contrast analysis by measuring edge sharpness in the captured image. It does not segregate pixels into halves but relies on image contrast in normal pixels.
ISP Process for PDAF:
Aspect | PDAF ISP Process | CDAF ISP Process |
Input | Phase detection pixels (split right/left halves) | Normal image pixels |
Key Operation | Phase difference extraction via dual-phase images | Contrast/sharpness computation from image data |
Lens Adjustment | Direct calculation of direction and magnitude | Iterative search for max contrast |
Speed | Very fast (milliseconds) | Slower due to sequential focus measurements |
Precision | Good, sometimes less precise in challenging scenes | High precision, especially for static subjects |
Choosing Between PDAF vs CDAF for Embedded Applications
The debate of PDAF vs CDAF is not about which is universally better, but about which is best suited for your application.
PDAF delivers high-speed autofocus with minimal latency. Use PDAF when speed and real-time tracking are critical. For example, in drones, robotics, AR/VR, or kiosks with live users.
CDAF ensures maximum sharpness in static scenes. Use CDAF when accuracy and cost-effectiveness are more important than speed such as medical devices, document scanning, and inspection cameras.
At Vadzo Imaging, we design and manufacture embedded cameras with both PDAF and CDAF AF technologies to meet diverse industry requirements. Whether you need an autofocus solution for kiosks, industrial automation, drones, or medical imaging, our team can guide you toward the right choice.
Check out our products:
Why PDAF vs CDAF Matters in Embedded Cameras
Choosing between PDAF vs CDAF in embedded OEM cameras comes down to application needs. If you are unsure which autofocus technology aligns best with your project, the experts at Vadzo Imaging can help you identify the right solution and provide end-to-end support for your camera requirements.
