Megapixels aren't everything: Why sensor size is crucial for good pictures

In the world of digital photography and surveillance technology, there is often talk of "high megapixel counts". The more megapixels, the better the image quality - right? It's not quite that simple. Especially with cameras in safety-critical areas - such as potentially explosive areas - it's not just the resolution that matters. An often underestimated factor is the size of the image sensor. In this article, we explain why sensor size is more important than many people think, why small sensors are still often used - and what this means for use in ATEX zones.

1. what are megapixels anyway?

One megapixel corresponds to one million pixels. A camera with 12 megapixels therefore delivers an image with 12 million pixels. That sounds impressive - but a high-resolution image is not automatically a good image. This is because image quality depends on several factors - such as light sensitivity, image noise and dynamic range - and this is precisely where the sensor size plays a decisive role.

2. sensor size: the secret hero of image quality

The image sensor is the "eye" of the camera. It converts the incident light into electrical signals. The larger the sensor, the more light it can capture - and that means:

✔️ better pictures in low light conditions

✔️ less image noise

✔️ greater depth of field control

✔️ More realistic colors and contrasts

A 12-megapixel sensor with a large surface area generally delivers significantly better images than a 20-megapixel sensor in a small space - simply because each individual pixel receives more light.

3 Why are small sensors used so frequently despite these disadvantages?

The answer is simple: cost and size.

Large sensors are significantly more expensive to manufacture - a high-quality 1-inch sensor can quickly cost 80 to 100 euros, while small standard sensors (e.g. 1/4" or 1/3") are available for less than 10 euros.

In addition:

🔹 Large sensors require larger lenses - this makes the camera bulkier.

🔹 Small sensors enable compact, cost-effective designs.

🔹 High megapixel numbers are easy to market on the data sheet - regardless of the actual image advantage.

For this reason, a compromise is often chosen, especially for low-cost systems or cameras in compact housings (e.g. ATEX compact solutions): Lots of megapixels, but a small sensor.

4. small sensors, many pixels - a compromise with side effects

When many megapixels are accommodated on a small sensor, each pixel has very little space. The result:

• Increased image noise
• Poorer performance in low light conditions
• Lower dynamics
• Stronger artifacts with digital zoom

Such limitations can be problematic, especially in safety-relevant applications such as monitoring hazardous areas. What use is a high-resolution image if details are blurred in the dark?

5 What you should consider with cameras for ATEX areas

The following applies for use in potentially explosive atmospheres:

The camera must be ATEX-certified.

🔸 The image quality must be reliable and meaningful - even in difficult lighting conditions.

🔸 Robustness and temperature behavior are crucial

It therefore makes sense not only to pay attention to the number of megapixels, but also to look specifically for cameras with larger sensors (e.g. 1/1.8" or larger) - even if they offer 'fewer megapixels' on paper.

6 Conclusion: Quality instead of quantity

Megapixels alone say little about image quality. Especially in professional applications - such as explosion protection - the sensor size is a decisive factor. A high-quality camera with a larger sensor often delivers significantly better results than a megapixel monster with a tiny chip.

7. how to recognize the sensor size in the data sheet?

The sensor size is usually specified in fractions of an inch - not as an actual physical size, however, but as a historically evolved, less intuitive unit. Typical specifications are as follows:

• 1/4"
• 1/3.2"
• 1/2.8"
• 1/1.8"
• 2/3"
• 1"

Important to know:

These values say nothing directly about the actual dimensions of the sensor! A "1/2.8 inch" sensor, for example, does not have a diagonal of 0.36 inches = 9.1 mm, but only about 6.4 mm. This is because the specification historically refers to old television picture tube formats.

Here are some examples with real sensor sizes (diagonal in mm):

Tip: The smaller the fraction (e.g. 1/1.8 instead of 1/3.2), the larger the sensor - and the better the image quality as a rule.