What is a pixel ? Resolution, megapixels and sharp photos
When you look at the technical specifications of a camera, there is often a number that catches your eye: 16, 21, 24 megapixels. The higher the number, the better? Not necessarily. And above all, do we really know what it means?
Pixels are everywhere. They make up every image we see on a screen and every photo we take. Yet this little word remains unclear to many. What does a pixel represent? What is the difference between resolution and megapixels? And above all, how can you tell if a photo will be really sharp?
What is a pixel?
Before understanding what 16 or 24 megapixels mean on a product sheet, we need to go back to basics: the pixel. It is to a digital image what a brick is to a wall or a tile is to a mosaic. It is the fundamental building block.
But in concrete terms, what does a pixel represent? And how does it influence what we see in a photo? Let us explain.
A pixel is a dot... but not just any dot
In a digital image, a pixel is a small dot of colour. It is usually so small that it cannot be seen with the naked eye. But when you zoom in on an image, these dots become clearly visible. They are what give shape to the photo, like thousands of coloured dots on a canvas.
Each pixel contains colour information. Red, green, blue, or a mixture. When placed side by side with millions of others, they form the image you see on a screen or in a printed photo.
A mosaic or fabric: images made up of small elements
To visualise what a pixel is, imagine a mosaic. Each tile is different, but together they form a complete scene. Or even better, think of a piece of fabric. From a distance, you see a solid colour. Up close, you can see the threads, the little strands. A pixel is the same. It's small, but essential for drawing the whole picture.
In a digital photo, the more pixels there are, the more accurately you can represent details. That's why the number of pixels is often highlighted in technical specifications.
A pixel does not have a fixed physical size
Contrary to popular belief, a pixel does not have a standard size in millimetres. Its size depends on the display medium. This could be a smartphone screen, a computer screen or even a paper printout. The same 3000 x 2000 pixel image may appear larger or smaller depending on where it is displayed.
Unlike film cameras, what matters with digital cameras is the total number of pixels and how they are distributed. This is called resolution.
What exactly is image resolution?
In the context of digital photography, resolution refers to the number of pixels that make up an image. It is usually expressed as two numbers: width x height. For example, a photo with a resolution of 1920 x 1080 pixels contains just over 2 million pixels.
This value gives an idea of the density of detail. The higher the resolution, the better you can capture subtleties, textures and nuances. When photographing a landscape, for example, this allows you to see the leaves of a tree in the distance. In a portrait, eyelashes or hair will appear sharper.
Tip: if you zoom in on a photo taken with a low-resolution camera, you will quickly see blurry squares. These are pixels. On a camera with more pixels, the image remains sharp for longer, even when zoomed in.
What are megapixels?
It's often the thing that catches the eye on a product sheet: the number of megapixels. We automatically associate a high number with better image quality. However, the reality is more nuanced. Megapixels matter, of course, but they aren't everything.
Before choosing a camera based solely on this criterion, it's useful to understand what these millions of pixels really mean and when they make a real difference.
How many pixels are in a megapixel?
Let's start with the basics. One megapixel (MP) is equal to one million pixels. It is a unit of measurement that summarises the total number of small dots that the camera's sensor can record when taking a picture. The more pixels there are, the more information the image contains.
For example, a 21 MP photo is approximately 5,000 pixels wide by 4,200 pixels high. That's more than 20 million dots placed side by side to make up the image. A 24 MP photo, on the other hand, is 6,000 x 4,000 pixels, which means even more detail.
These figures reflect the ability to reproduce scenes accurately. The higher the definition, the more you can zoom in on the image, print in large format or crop a specific area without losing visible quality. This is what makes megapixels useful, especially when you want to maintain a good level of sharpness in all situations.
Why have more megapixels?
Having more megapixels can be a real advantage, especially if you like to crop your photos after shooting, make large prints or zoom in on details in a scene. In these cases, higher definition offers more freedom.
But that's not always enough. A 24 MP image can still appear blurry if the camera moves slightly or if there is not enough light when the photo is taken. That's why you shouldn't rely solely on the number of megapixels to judge the quality of a photo.
Concrete examples to better understand the importance of megapixels
Take the AgfaPhoto Realishot DC5200, a compact camera with a resolution of 21 megapixels. This is a good balance for a wide variety of uses without technical complexity.
With 21 MP, you can capture detailed souvenir photos on holiday, with your family or at an event. The image contains enough information to print in standard formats, such as 10x15 cm or A4, without any visible loss of quality. This is also useful if you want to crop a photo slightly after shooting without degrading the image.
In addition, an image captured in 24 megapixels offers even more scope. This level of definition is ideal if you like to zoom in on specific details or rework the composition of a photo in post-processing. For example, you can isolate a face in a group scene or refocus a landscape while maintaining sufficient sharpness for printing, even in larger formats.
Finally, a camera with 16 MP is perfectly suited for video use, especially if it can film in 4K. In this case, the priority is not the total number of pixels in a photo, but the ability to deliver smooth, stable and well-defined images in video. This type of camera often focuses on overall balance. Stabilisation, image processing, light management. All these elements contribute to producing a sharp image, even without focusing on the megapixel race. The Realishot VLG4K-DIG from Agfa Photo is a perfect example.
Resolution and display: how to read a technical data sheet without making a mistake?
When you read a camera's specifications, you often see impressive figures: 21 MP, 6000 x 4000 pixels, A3 printing, 4K video. But without the right benchmarks, these values can be confusing.
Understanding what resolution means, in photography as in printing, allows you to make a more informed choice and avoid some common mistakes.
Pixel density varies depending on the camera
It is not enough to compare the megapixels of two models to determine their quality. Two cameras with 24 MP can produce very different results. It all depends on the size of the sensor and the quality of the lens.
On a compact camera, the pixels are often closer together than on an SLR. This can result in a little more noise or loss of detail in certain lighting conditions. Conversely, a good compact camera with a high-quality lens can produce very convincing images.
It is therefore important to consider resolution in the overall context of the camera.
How does an image adapt to a screen?
When you look at a photo on a smartphone, tablet, computer or television, the image is automatically adjusted to the size of the screen. Even a 24 MP photo will be displayed in a smaller format, as no standard screen can display all the native pixels at once.
What you see on the screen is therefore often a reduced version of the photo. This is why an image may look perfectly sharp on a phone but a little less precise when printed in large format.
It is also possible that a file that is too large may be compressed when sent or shared online, reducing its apparent quality.
Don't rely solely on megapixels
One of the most common pitfalls is choosing a camera solely because it has a high megapixel count. However, the quality of a photo also depends on other essential factors. You need to consider the quality of the sensor, the type of zoom (optical or digital), the ability to handle light well, and the responsiveness of the camera, particularly in terms of shutter speed and stabilisation.
Let's take a concrete example: the Realishot DC8200 offers 18 MP. But its main advantage lies elsewhere. It has an 8x optical zoom, which allows you to get closer to a subject while maintaining sharpness. This type of zoom, which acts directly on the lens, preserves details, whereas a digital zoom simply enlarges the image without improving its definition.
It is therefore not just the number of pixels that counts, but how the camera uses them to reproduce a faithful, sharp and well-balanced image.
Understanding pixels to choose the right camera
A pixel is a starting point. Millions of tiny dots form a complete image that can be seen on a screen or on paper. The more pixels there are, the more detail can be captured, but you still need to know how to use them.
Megapixels are important, but they alone do not guarantee a good photo. The light, stability, sensor and quality of the lens are just as important. A sharp image depends as much on the camera as on how it is used.
To choose the right model, you need to look beyond the numbers. Reading a technical specification becomes easier when you understand what pixels, resolution and zoom mean. This allows you to better tailor your choice to your needs. A better understanding of the basics is the key to getting the most out of digital photography without getting lost in technical terms.