How much resolution does a camera need?

The Game Boy Camera features 0.014 megapixels. Meanwhile, Nikon’s first professional camera, the D1, offers just 2.7 megapixels. Today, professional cameras offer between 24 and 100 megapixels, a pretty wide range. But how much resolution is ideal? There’s no hard-and-fast answer. It depends what you need the camera for and how you view photos.

It’s also important to be flexible when it comes to resolution, as a lot depends on the technology used. For instance, you need to bear in mind whether or not sensor technology, lenses, computing power and data storage are adequate for different resolutions.

Sensor and pixel size

The noughties saw the launch of compact cameras with ever-higher resolutions. Although this initially marked great progress, it increasingly turned into a hollow marketing ploy. We soon learned that a camera can also have too much resolution. The problem was the combination of high resolution and a very small sensor. This resulted in minute pixels.

The larger each individual pixel, the more light-sensitive it is. As a result, these pixels display colour and brightness more accurately in low light, leading to less noise. Light-sensitive pixels also cope better with large differences in brightness within the image. On a large sensor, individual pixels are bigger at the same resolution. And often even at a higher resolution.

But how can we compare the pixel size on sensors of varying dimensions? If one of the sensors is a full-frame sensor, use the following formula. Divide the resolution of the full-frame sensor (rFF) by the crop factor of the other sensor squared.

In a sample calculation with full-frame camera EOS R5 and APS-C camera EOS R50 – both Canon – the EOS R5 has 44.7 MP. The crop factor for Canon APS-C cameras is 1.61. And so, I divide 44.7 MP by 2.6 (1.61 squared), which gives 17.2 MP. This is how much – or little – resolution an APS-C camera requires in order to produce pixels that are the same size as on a full-frame camera. Consequently, the Canon EOS R50 with 24.2 megapixels already has smaller pixels than the Canon EOS R5.

You can also convert the equation so it works in the opposite direction. Starting with the R50: 24.2 × 2.6 ≈ 63. As a result, a Canon full-frame camera would only have smaller pixels than the Canon EOS R50 from 63 megapixels onwards.

The compact camera Sony RX100 with its 20 megapixels has such small pixels that 146 megapixels would be enough in full format.

The difference between Fujifilm and Hasselblad’s full and medium format isn’t that much. Their 100 megapixel sensors feature smaller pixels than the Canon EOS R5.

In summary, full-frame sensors can have a really generous number of pixels. On the other hand, when you’re dealing with smaller sensors, you quickly reach a critical range.

These rules can’t be applied directly to smartphones as they work differently. The latter feature small sensors but high resolutions. Thanks to various tricks, including multiple exposure and pixel binning, they still achieve acceptable image quality. Their high resolution is used to zoom digitally and still achieve sufficiently high resolution. However, I’m not going to delve into smartphone distinctions in this article – we’re just focusing on traditional cameras.

Video resolution: reserves required

Video resolutions are standardised so it’s clear which resolutions The most common standards are:

• Full HD: 1920×1080 = 2,073,600 pixels ≈ 2.1 MP
• UHD (4K): 3840×2160 = 8,294,400 pixels ≈ 8.3 MP
• UHD-2 (8K): 7680×4320 = 33,177,600 pixels ≈ 33.2 MP

This means that every present-day camera meets the requirements for 4K. That’s not the case with 8K. According to the above calculation, a camera would need at least 33 megapixels. But even that’s not enough. This is because practically all cameras also used for photography have a sensor with an aspect ratio of 3:2 or 4:3. As a result, only part of the sensor is used for videos in 16:9 format.

This gives the following minimum resolution for 3:2 sensors:

• 3840×2560 = 9,830,400 pixels ≈ 10 MP
• 7680×5120 = 39,321,600 pixels ≈ 39.3 MP

And with 4:3 sensors:

• 3840×2880 = 11,059,200 pixels ≈ 11 MP
• 7680×5760 = 44,236,800 pixels ≈ 44.2 MP

But this is only the absolute minimum. For optimum sharpness, the resolution needs to be higher. This is because minimum resolution doesn’t allow downscaling.

Downscaling – or why more is better

A camera’s resolution should be higher than the resolution of the final image. This applies to videos as well as photos viewed on screen.

For example, if you have an 8-megapixel camera, it can’t produce the same sharpness as an 8-megapixel image downscaled from a higher resolution. The reason for this is the RGB filter. Photosensor pixels can only capture one colour out of red, green or blue at a time. The remaining colour values have to be calculated from the surrounding pixels. The process is called demosaicing and leads to blurring.

While downscaling, each pixel is also recalculated based on neighbouring pixels – a process called interpolation. But because the resolution is higher, more information can be included.

The resolution doesn’t need to be a lot higher than the target resolution. For videos, it can even be better to keep it low. Images are quicker to read so there’s less rolling shutter. If the sensor is read 60 times per second and an image is recalculated each time, large amounts of data can also lead to overheating.

Image noise: pixel size versus downscaling

Downscaling also has another positive side effect: image noise is smoothed out, since interpolation is used to match the colour and brightness of the surrounding pixels. Noise is nothing more than a random, unwanted deviation in colour and brightness. This is levelled out by reducing the resolution.

In contrast to sharpening, this effect is significantly stronger at high resolutions. With high-resolution sensors, more of the image noise disappears when downscaled to the same target resolution.

However, as mentioned at the beginning, large and therefore light-sensitive pixels produce less image noise – a compelling case for lower resolution. Which effect is more important? Does a picture with a high resolution produce even less noise when both are downscaled to UHD?

Not normally. The advantage of larger pixels outweighs image noise. For example, the Nikon Z6 II with 24.5 MP and the Nikon Z7 II with 45.7 MP at ISO 25,600. In the direct comparison above, you can see the original size. In this instance, the high-resolution Z7 II is much noisier. If it’s scaled down to the same size as the Z6 (below), the noise is still slightly higher. But the image is sharper.

This test scenario comes from dpreview.com. You can access it here and play around with parameters such as ISO or other cameras. It’s a similar scenario with the Canon EOS R5 and R6.

However, the blanket statement «sensors with less resolution produce less noise» is by no means always true. It’s only really accurate to compare sensors of the same design. For instance, an old sensor from the noughties probably produces more noise than a present-day sensor with a high resolution, even at a lower resolution. And it goes without saying that the sensors need to be the same size.

Viewing on screen

A full HD screen only shows about 2 megapixels, while a 4K screen only displays 8. It takes an 8K screen (33 megapixels) to display the resolution of today’s cameras.

However, it all boils down to the same thing. You can only achieve optimum sharpness by downscaling from a larger image. If you don’t, the graphics chip will do it for you – but potentially not as well since it has to do it in real time.

More importantly, you can zoom in on a screen. This is awkward on a TV, but on all other screens, especially touchscreens, it’s easy as pie. That’s when there are noticeable differences between photos with 8 and 50 megapixels.

Printed photos

You can’t zoom in on printed photos, so the resolution rarely needs to be higher than 10 megapixels. Even large posters don’t require infinite resolution. You’re looking at them from further away, so the pixel density can be lower. At a viewing distance of five metres or more, 20 to 30 dpi is sufficient rather than the 300 dpi typical of photo albums.

You can easily achieve the specified dpi values, even with 10 megapixels. Of course, more is better in case the poster gets viewed up close. But high resolution isn’t necessary for printing.

Cropping images

A big advantage of a higher resolution is if I use a section of an image, it’s still sharp enough. Every now and then, people tell me I wouldn’t have to crop my images if I could take proper photos. But that’s nonsense.

I remember the shoot in the BMX park. A lot of things happen so quickly that it’s impossible to think about image composition. You simply aim at the centre of the picture and hope the subject is completely in it. The chances of this happening are much better if you leave some space all around.

Another example is birds in flight with unpredictable changes of direction. Generally speaking, wild animals don’t give a damn about your composition. You have to take what you get. And some things are simply too far away. With high resolution, you can still make something of the shot; but you can’t with a lower resolution.

When it comes to photographing large buildings, it’s a simpler technique. If you want to capture them in full frame without a tilt-shift lens, you’ll end up with falling lines. If you hold the camera straight, you’ll have to crop out a large part of the image afterwards.

There are also instances where an image needs to work for different page formats. When you take the photo, you don’t necessarily know if the magazine requires the image in portrait or landscape format. Obviously, you can do both in the studio. But in sports photography, you get to a moment where you have to choose between portrait and landscape – and then crop, which only works if there’s enough space around the subject.

In short, there are countless instances where you’d need to crop after shooting. And that’s when having extra resolution up your sleeve really pays off.

Data volume: not a problem in today’s world

The lower the resolution, the less data needs to be processed. For a long time, only cameras with relatively few pixels were able to achieve high continuous shooting speeds, which are key for sports and action photography.

This began to change in 2021, coinciding with the release of the Sony Alpha 1. It boasts 50 megapixels and shoots 30 images per second. However, this camera also set you back 8,000 francs or euros at the time. Those who couldn’t or weren’t prepared to reach this far into their pocket had to choose between high speed and high resolution.

These days, you don’t have to make this compromise. The Canon EOS R5 II and Nikon Z8 cost significantly less than the Sony Alpha 1 and also offer high resolution at high speed. Even the Canon EOS R7, with a price tag under 1,500 francs, manages 30 images per second with a resolution of at least 33 megapixels.

Professional sports cameras do still tend to come with low resolution. The Canon EOS R1 and Sony Alpha 9 III are around 24 megapixels. But these are tools for professionals with very specific requirements. The global shutter on the Sony camera just isn’t available in a higher resolution (yet). Canon’s flagship also meets special requirements with its sky-high frame rates and extreme exposure situations. The aim here is to get that little bit more out of a particular area. If you don’t necessarily need that but want to use the camera for other things, you’re better off with a higher resolution.

High resolution alone won’t make the image sharper

It’s harder to get the full potential out of a camera with very high resolution. For the image to really be sharper and show more detail, it hinges on two things.

For one, the lens needs to be sharp enough. Some don’t manage a resolution of 50 or more megapixels. Not even when dimmed. With an open aperture, slight blurring is almost always visible in the corners of the image.

But newer lenses have been adapted to modern resolutions. This means you can enjoy a higher resolution even if the lens doesn’t capture the entire image, since you can still see a bit more detail. And let’s be honest, when do you really need the corner of the image to be sharp with an open aperture?

Secondly, you need to prevent shaking and motion blur, as high resolution reveals even the faintest sign of blurring. The tolerance range is greater at a low resolution. You can compensate for camera shake with a better image stabiliser. When it comes to motion blur, the only way to solve it is by shortening the exposure time.

However, I wouldn’t say this is a disadvantage or a point in favour of lower resolution. If you scale to the same target resolution, for example UHD, the blurring is equally visible in both cases.

Verdict: high-resolution all the way in full format

The advantages of higher resolutions are more flexibility in post-processing and images with greater detail. This applies to 8K screens as well as to any that you can zoom in on. 8K video is only possible with high resolutions starting at 40 megapixels.

The disadvantages of sensors with a high resolution are slightly lower dynamic range and higher image noise. You can compensate for the latter slightly by scaling down. For a long time, the immense amount of data also caused problems. However, this isn’t a big issue in 2024. High-resolution cameras are also fast and durable.

With the current state of technology, I prefer 40 or 50 megapixels in full format to low resolutions such as 24 megapixels. For an all-round camera, the advantages of higher resolution outweigh the disadvantages. This can be different for special use cases, as shown by some professional sports cameras. I’m also sceptical about smaller sensors, such as the APS-C format, where 25 megapixels still seem more appropriate in my eyes.