Sony IMX675 vs. OmniVision OS04J10: Which Sensor Is Better for Rear Dash Cams?

When you're shopping for a dash cam, specs like "8 megapixels" or "4 megapixels" sound straightforward.

Most people naturally assume that higher megapixels must mean clearer, sharper recordings. But during real-world testing—especially when comparing sensors like the Sony IMX675 and OmniVision OS04J10—we discovered that image quality doesn't follow that simple rule.

Conclusion: OmniVision OS04J10 Is Better for Rear Dash Cams.

In fact, a lower-megapixel sensor can sometimes capture clearer details than a higher-megapixel one. Why does this happen, and what does it mean for choosing a rear dash cam?

Let's break down this counterintuitive finding in the simplest way possible.

Usually in these situations: - Rear-end collision at night - The car behind you has its headlights on, and you need to clearly see its license plate.

- Parking lot surveillance - In dark underground parking garages, you need to be able to see if anyone is around.

- Lane change dispute - You need to be able to clearly see cars in the left, center, and right lanes simultaneously.

- Minor collision - Even in poor lighting, you need to be able to recognize the color and features of the cars.

Statistically, more than half of these scenarios occur in poor lighting conditions.

1. Clear visibility in low light - It should work in the dark at night or in underground parking garages.

2. Not afraid of strong light - The license plate should be seen when illuminated by headlights.

3. Clear visibility even at an angle - The license plates of cars in adjacent lanes must also be clearly captured.

For drivers who want to better understand the role of a rear camera on a dash cam and when it becomes essential, you can read our detailed guide: Do You Really Need a Rear Dash Cam？

Evaluation metric: Simultaneous clarity of left, center, and right lane license plates

OS04J10 performance:

• ✅ Left lane: clear
• ✅ Center lane: clear
• ✅ Right lane: clear

IMX675 performance:

• ✅ Center lane: clear
• ⚠️ Left and right lanes: sometimes blurry

The OS04J10's large pixel count gives it a significant advantage in capturing images of adjacent lanes, primarily for three reasons:

Reason 1: Faster shooting, less blurry

• Larger pixels allow for faster light capture, resulting in a quicker image.
  
  
  • When a car in the adjacent lane speeds past you, it's like taking a picture of an athlete; the faster the shutter speed, the less blurring occurs.

Reason 2: Better Edge Image Quality

• The larger the sensor, the less image quality loss occurs at the edges of the image(i.e., the left and right lanes).
  
  
  • Just like how a full-frame camera uses a larger image circle to keep the corners sharp, a small-format lens has a much tighter image circle, so the edge light gets squeezed and the corners tend to turn blurry.

Reason 3: Clear Even When Viewed at Angles

• Larger pixels mean less noise and a cleaner image.
• A cleaner image means that even if the license plate is angled or not directly facing the camera, the text will still be clearly visible.
  
  
  • Just like a high-resolution photo, details won't be blurry when zoomed in.

If you get into an argument with another car while changing lanes, then:

• Regular dashcam: can only clearly capture the license plate of the car directly in front.
• OS04J10: can clearly capture the license plates of cars in the left, middle, and right lanes.

This makes the whole incident more complete and the evidence more substantial.

Evaluation metric: Clarity of license plate of the vehicle in front under backlight

[Real Test Comparison Image 2: Nighttime Backlit License Plate Capture]

OS04J10 performance:

• ✅ License plate areas are clear, with all details preserved
• ✅ Handles strong light well, no overexposure

Sony IMX675 performance:

• ⚠️ License plate areas often appear washed out
• ⚠️ Details in dark areas are frequently lost

Larger pixels control "charge overflow" better, preventing blurry highlights. Nighttime backlighting is the most demanding scenario for sensors, and larger pixels have two advantages in this regard:

• Larger charge storage capacity: Larger pixels can store more charge (technically called "full-well capacity").
  • Just like water in a large bucket is less likely to overflow, so it won't become blurry even under strong light.
• Stronger light-catching ability: Even in reflective areas, larger pixels can still capture enough signal, preserving license plate details.

Backlighting is the most common scenario in rear-end collisions. This capability directly determines whether the footage captured by your dashcam can be used as valid evidence.

Larger pixels offer clear advantages in low-light imaging:

• Easier to fill with light → Brighter images
• Capture enough light faster - Shorter exposure times - Less motion blur
• Lower noise when fully filled - Cleaner, more detailed night footage

These benefits come from the fundamental physics of image sensors. The essence of sensor imaging is the process of converting photons into electrical signals. A larger pixel works like a bigger "bucket for catching light."

More incoming photons per unit time means stronger signals, better brightness, and less noise-especially in nighttime or low-light environments. We can imagine it as "catching water on a rainy day":

• IMX675:like many small cups—there are more of them, but each one is small (2.0 μm).
  
  
  • When the rain is light, small cups collect very little water.

• OS04J10:like fewer but larger bowls or buckets (2.9 μm).
  
  
  • Even with light rain, bigger bowls naturally collect more water.

At night, the light is like light rain; a large bowl catches more light than a small cup, so the OS04J10 performs better in low light.

For more details, see this in-depth guide on sensor size.

Larger pixels provide a significantly higher Signal-to-Noise Ratio (SNR), resulting in cleaner, clearer, and more usable footage in low-light conditions.

• Small pixels: Capture very little true signal → noise dominates → muddy, grainy image
• Large pixels: Capture more true signal → noise proportionally lower → cleaner image with clearer details.

What is Signal-to-Noise Ratio?

Signal-to-Noise Ratio (SNR) represents the ratio between "useful information" (signal) and "garbled noise." In imaging and video recording, a higher SNR means clearer, more usable footage.

Why larger pixels improve SNR

One key method to enhance SNR and reduce noise is using larger pixels:

• Larger pixels capture more true light signal → brighter images
• Retain more details in dark areas → better usability under complex lighting

Practical benefits in driving scenarios

Dark or challenging lighting areas often require higher visibility than bright areas:

• Parking monitoring: Detect movements in corners of parking garages
• Passing through tunnels: Distinguish vehicles in inner lanes
• Backlighting situations: Recognize license plates partially shadowed by headlights

Imagine raindrops containing dirt:

• "Clean water" = true image signal
• "Dirt" = noise

Larger pixels act like bigger buckets, catching more "clean water" per unit time and reducing the relative impact of dirt, resulting in a clearer, more detailed image, especially in dark or complex lighting environments.

IMX675: Small cups (small pixels)

• In light rain, only a small amount of water is collected
• But the dirt mixed in remains the same
• Result: very little clean water and a high proportion of dirt → a muddy cup that’s hard to see through

OS04J10: Large bowls (large pixels)

• Even with light rain, the bowl collects more water
• The amount of dirt stays the same
• Result: more clean water and a lower proportion of dirt→ slightly muddy but still visible

This is why in dark environments such as underground garages or tunnels, the OS04J10 can reveal the people and vehicles in the corners—while the IMX675 may produce a blurry, noisy image instead.

For dash cams, pixel is not only the core factor that determines image quality. Sensor area, pixel size, and low light sensitivity are priority metrics for engineers.

Using the OS04J10's light-sensing area as the 100% baseline, the IMX675 reaches only about 45% of that area.

As mentioned in the above practical use cases, the OS04J10 has a more significant advantage in rear camera performance.

The most important function of a dashcam is to capture clear and visible footage in critical moments.

The key component determining image quality is the "Sensor." It's like the dashcam's "eyes."

When developing the next-generation rear camera module, the RedTiger engineering team conducted extensive testing on multiple sensors and ultimately chose the OmniVision OS04J10 instead of the Sony IMX675.

This may seem counterintuitive, but our team's philosophy is simple: we don't chase the best-looking specs, we believe in the best real-world performance.

The most important aspect of a rear camera is its ability to capture clear images at night and in complex lighting conditions, rather than ultra-high definition during the day. Based on this positioning, the OS04J10's large pixel design is perfectly suited.

When choosing a dashcam in the future, pay attention to the following three points:

1. More pixels do not necessarily mean better image quality, especially at night.
2. Rear cameras are mainly for nighttime and backlighting, not daytime use.
3. For dashcams, larger pixels are more practical for the rear camera.

When choosing your next dashcam, you might want to look beyond the 'number of pixels' and also consider 'pixel size' and 'sensor size.' 

Thank you for reading this article.