Stacked Sensors Explained: What Photographers Need to Know

Stacked sensors are a big step forward in camera tech. But how is this approach different from the old designs? Modern stacked CMOS sensors go beyond the backside-illuminated (BSI) idea. They add an image signal processor and fast memory right into the chip, resulting in a significantly faster readout.

So what are these benefits to you as the photographer? You receive less rolling shutter, better burst shooting, and faster autofocus. These are major pluses for capturing sports, wildlife, or anything moving fast.

Key Takeaways

Stacked sensors layer multiple components into a single unit.
The technology incorporates image processors and memory directly into the silicon structure.
Offer significantly faster readout speeds.
Reduced rolling shutter distortion when capturing moving subjects
Superior burst shooting capabilities
One of the most significant recent advancements in digital imaging

What Is a Stacked Sensor?

Unlike old sensors, stacked sensors are what we call a 3D design. Its layout and design are different; the sensor is the imaging system, rather than dispersing it throughout the camera.

How Does a Stacked CMOS Sensor Work?

Stacked CMOS sensors have a layered design. The top layer captures light and turns it into electrical signals.

The middle layer handles the electrical signals. It has the circuitry to read and process the signals. This layer converts the signals into digital data.

The bottom layer is a fast DRAM memory buffer. The bottom layer functions as a fast DRAM memory buffer, storing data quickly before transferring it to the main processor. Avoiding delays for rapid shooting.

When you take a photo, light hits the top layer. The signals then move down to the middle layer for processing. The data goes to the DRAM buffer, then to the main processor for final touches before saving.

What Makes a Stacked Camera Sensor Different?

The construction and capabilities of CMOS sensors and stacked sensors differ.

Sensor Type	Architecture	Readout	Rolling Shutter	Advantages
Traditional CMOS	Single layer with mixed components	Slower	Significant	Cost effective manufaturing
BSI CMOS	Single layer with optimized light path	Moderate	Moderate	Improved light sensitivity
Stacked CMOS	Multi-layer with seperate functions	Very fast	Minimal	Superisal speed and processing
global shutter	Specialized design with per-pixel storage	Fast	None	Distortion-free motion capture

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Benefits of Stacked Image Sensors

Stacked sensors read data quickly, unlike old sensors that read row by row.

Reduced rolling shutter: The fast sensor readout minimizes distortion, even for fast-moving subjects.
Silent shooting: Electronic shutters eliminate mechanical shutter noise, ideal for action.
Improved autofocus: Stacked sensors enable faster focus adjustments for better tracking.
Enhanced video: Achieved through smoother motion and reduced distortion.

Surprisingly, stacked sensors also save battery life, by working more efficiently because their components are closer together.

Advantages of Stacked Sensors for Digital Cameras

Stacked sensors bring speed, performance, and quality improvements. Thanks to separating the photodiode layer from the processing circuitry.

Improved Image Quality

Stacked sensors boost image quality by having a higher dynamic range. Plus, the new design reduces electronic noise; your photos are cleaner in low light. Traditional sensors get hot, often causing noise.

What does this mean for you? Well! Better colour, details, low noise in higher ISO, and faster frame rate in burst mode.

Faster Readout Speeds

Stacked sensors read data much faster. Fast readout speeds also help with silent shooting. The rolling shutter effect is less of a problem. Meaning you can shoot quietly without distortion.

Feature	Traditional CMOS	BSI CMOS	Stacked CMOS
Readout speed	Slow 5-10 FPS	Moderate 10-15	Fast 20-30 FPS
Rolling shutter	Significant	Moderate	Minimal
Silent Shooting	Limited distortion	Usable for slow shutter	Practical for most actions
Flash sync speed	limited 1/200	Limited 1/250	Enhanced 1/500

Video shooters greatly benefit from enhanced readout speeds. The reduced rolling shutter effect means less distortion.

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Higher Dynamic Range

The ability to capture scenes with proper exposure in both light and dark areas depends on the dynamic range of the camera.

Why do we care? You do want better contrast in your photos? For us landscape and architecture photography enthusiasts, stacked sensors provide a significant advantage. They can do multi-shot HDR quickly. This extends dynamic range without ghosting or alignment issues.

How Do Stacked Sensors Compare to Traditional Sensors?

Stacked sensors have changed digital camera tech. But how do they stack up against old sensors? Knowing the differences helps when you buy a new camera. It also shows how tech has improved your photos.

Understanding the Differences Between Stacked and BSI Sensors

BSI (Back-Side Illuminated) Sensor:

Purpose: Improves light capture efficiency.
How it works: In a BSI sensor, the photodiodes (light-sensitive part) are placed on top of the metal wiring layer. This allows more light to reach the sensor directly, reducing light blockage.
Improvement over: Traditional FSI (Front-Side Illuminated) sensors where wiring partially blocks incoming light.
Result: Better low-light performance, higher sensitivity, and less noise.

Stacked Sensor:

Purpose: Improves speed, processing power, and design flexibility.
How it works: One layer for the pixel array (photo diodes).
Another layer(s) for processing circuitry or memory (like DRAM).
The layers are vertically stacked and connected through through-silicon vias (TSVs).

🔍 Result: Faster readout speeds, more advanced image processing on-chip, and support for features like high-speed burst, 4K/8K video, and reduced rolling shutter.

Use Case in Devices

BSI-only sensors are found in many smartphones and consumer cameras due to improved image quality in a compact form.
Where are they used? In high-end smartphones, DSLRs, mirrorless cameras, and action cams that require fast autofocus, slow-motion video, and real-time processing

Do They Overlap?

Yes! Most modern stacked sensors also use BSI technology—so a stacked sensor is often a BSI sensor with extra layers added for performance.

Sony’s latest “stacked CMOS” sensors are both BSI and stacked, offering the benefits of both technologies.

...Bob

Full-Frame Cameras and Stacked Sensor Technology

Full-frame cameras already offer top-tier image quality, but when paired with stacked sensors, they unlock a whole new level of speed, precision, and performance.

Faster Readout Speeds: Reduce data read time, which is essential for processing the larger pixel count of full-frame sensors.
Reduced Rolling Shutter: Minimizes distortion in fast-moving scenes by reading the entire sensor much faster.
Improved Autofocus Performance: Enables quicker data flow to the processor, enhancing subject tracking and eye detection.
Better High-Speed Shooting: Supports rapid burst rates (20–30 fps) even at full resolution, perfect for action, wildlife, and sports.
Enhanced 4K/8K Video Recording: Efficient data handling and heat management allow longer, smoother high-res video capture.
Silent Shooting with No Compromise: Electronic shutters operate cleanly without banding or distortion, even under LED lighting.
More Efficient Use of Processor Power: Fast sensor output frees up the processor for advanced functions like AI tracking and image stabilization.
Greater Dynamic Range Potential: Separating imaging and logic layers helps maintain cleaner signals, boosting image depth and detail.
Optimized Eye and Subject Detection: More frames and data per second improves autofocus accuracy and tracking in real time.
Future-Proofing for Pro Features: Enables cutting-edge tech like global shutters, fast-refresh EVFs, and advanced computational tools.

How to Choose a Camera with a Stacked Sensor

When you’re looking for a camera with a stacked sensor, knowing what matters most can save you money.

But do you really need this advanced tech? Knowing what you need helps you choose the right camera for your photography.

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Key Features to Look for in a Stacked Sensor Camera

When shopping for a camera with a stacked sensor, look at more than just the sensor.

Check how the viewfinder works during fast shooting. Stacked CMOS sensors let you see your subject even when shooting fast. This functionality varies between brands, so test it before you buy.

Buffer capacity is also important. Even with fast sensors, your camera needs enough memory for continuous shooting. See how many RAW images it can handle before buffering starts.

Autofocus and advanced tracking and subject recognition are where they stand out. Compare different cameras based on:

The accuracy of eye/face detection is a key factor to consider.
Subject tracking persistence.
The camera has the capability to focus in low-light conditions.
Focus on acquisition speed.

Videographers will love stacked camera sensors for high frame rates and less rolling shutter. Check if the camera can record in 4K or 8K at various speeds.

Understanding Sensor Design and Its Importance

The image sensor is crucial for converting light into digital information. Different designs focus on different aspects, like speed and processing.

Early cameras used CCD sensors for excellent image quality, but they used a lot of power. Now, most cameras use CMOS technology. Standard CMOS sensors are suitable for everyday photos. BSI CMOS sensors improve light sensitivity and speed.

Stacked CMOS sensors add memory and processing behind the light-sensitive layer. This makes data processing faster, ideal for action shots and video.

When evaluating sensor design, consider how it affects image quality. Look at dynamic range, low-light performance, readout speed, and rolling shutter control.

Image Quality factor	Standard CMOS	BSI CMOS	Stacked CMOS
Dynamic Range	Good	Very Good	Excellant
Low light performance	Moderate	Good	Very Good
Readout Speed	Slow	Moderate	Very Fast
Rolling Shutter Controls	Poor	Moderate	Excellant

Evaluating Different Types of Camera Sensors for Your Needs

Choosing the right sensor depends on your photography needs. Think about your subjects and your shooting style to see if stacked CMOS sensors are worth it.

Sports and wildlife photographers benefit they allow for fast shooting and minimal viewfinder blackout. Event photographers also find these features useful.

Landscape, portrait, and studio photographers might prefer BSI sensors. These genres often value image quality over speed. BSI sensors offer a slight edge in dynamic range.

Consider your budget, stacked cameras sensor are more expensive. Ask yourself if the benefits are worth the cost.

Think about the whole camera system, not just the sensor. Lens selection, ergonomics, and compatibility are important for your photography experience.

Conclusion

Stacked sensors bring real improvements to today’s cameras. They make shooting faster, clearer, and better for action and video. While they aren’t for everyone, knowing how they work can help you choose the right camera for what you love to shoot.

They’re especially useful if you need fast autofocus, high burst speeds, or smooth 4K and 8K video. For sports, wildlife, or event photography, stacked sensors offer a big advantage. Even if you’re not ready to buy one now, it’s helpful to understand the technology. That way, you’ll be better prepared for your next camera upgrade.