Megapixels, optical zoom and lens aperture are numbers that directly influence the quality of a cell phone camera. But you need to know how to interpret them: bigger is not always better. Understand, below, the main technical specifications that will help you choose the best smartphone based on photo quality.
How many megapixels do I need?
A 10 megapixel camera is enough for most people. Despite being widely publicized by manufacturers, this specification has little impact on image quality and is not currently a technological limitation, as even basic cell phones can have cameras of 50 MP or more.
The megapixel only defines the resolution of a photo captured by the sensor, with 1 million pixels equivalent to 1 MP. Instagram, for example, only displays photos up to 1080×1350 pixels, that is, less than 1.5 MP. Therefore, even if your camera has 10 MP, the photos will be reduced when sharing.
Fewer megapixels are required for specific applications. A good quality 12 MP photo can even be printed on large paper, measuring 36×24 cm. A 4K video only requires a sensor capable of filming at 3840×2160 pixels, that is, 8.3 MP.
High-resolution sensors, such as 64, 108, or 200 megapixels, can capture more detail or allow for larger print sizes. Additionally, certain devices feature pixel binning technology, which combines information from multiple adjacent pixels into a single pixel, improving definition in low-light conditions.
However, noise level, lens sharpness and light sensitivity are factors as important as resolution and are not measured by the amount of MP. So the number of megapixels is just the beginning. And perhaps the least important in your research.
The bigger the image sensor, the better?
Generally yes. The image sensor is responsible for capturing the light that comes from the lens. If the image sensor area is larger, it can theoretically capture more light, which results in more detailed images and improves the camera’s performance in night photography and low-light conditions.
The size of the sensor is expressed in a fraction of inches in the device’s technical data sheet, with numbers such as 1/3, 1/2.3 or 1/1.5. Note that we are talking about fractions of numbers smaller than 1, so the smaller the second number, the larger the size.
Simpler cell phones usually have sensors with sizes close to 1/3 inch, while more expensive ones can reach 1/1.5, 1/1.3 or even 1 inch. It is worth remembering that smartphones can have multiple sensors and not all of them are used to capture a photo, such as depth sensors and LiDAR.
Why do cell phones have more than one camera?
A cell phone with three, four or more lenses tends to be more versatile than a cell phone with a single lens. This is because other cameras can take photos with a different appearance (of distant or very close objects) or improve the performance of the main camera (for example, measuring depth to blur the background).
The main types of camera lenses and sensors in phones are:
- Ultrawide lens: has a very wide field of view and allows you to capture panoramic images or photographs in tight spaces where it is difficult to move away from the scene;
- Macro lens: designed to take extremely detailed photos of very close objects, such as insects, flowers and water drops;
- Telephoto (or telephoto) lens: captures distant objects, offering optical zoom capability without significant loss of quality;
- Periscope lens: uses a system of mirrors parallel to the device’s body to reflect light to the sensor, allowing greater optical zoom than simple telephoto lenses without greatly increasing the thickness of the cell phone;
- Depth sensor, ToF (Time-of-Flight) or LiDAR: calculates the distance between the camera and different objects in the scene, improving the accuracy of the bokeh effect and face detection in portrait mode photos;
It is worth mentioning that some smartphones can combine functions in the same lens, such as the Galaxy S23 Ultra, which uses a telephoto lens to take macro photos.
What is the difference between optical and digital zoom?
Optical zoom uses the camera lens to zoom in on a scene, while digital zoom is software enlargement of the image. The specification to be observed by those who want to take photos of distant objects is the optical zoom.
In optical zoom, the number that follows the “x” represents, in times, how much greater the focal length is than that of the cell phone’s main camera.
Take for example a cell phone whose main lens is 18 mm. If the telephoto or periscope lens has a focal length of 54mm, the optical zoom is 3x. This means that an object will be three times “closer” to the camera when you take a photo at maximum optical zoom.
Digital zoom consists of digitally enlarging and cropping an image, in the same way you would do in Photoshop or another editor. It is not very interesting because it reduces the quality of the photo. Furthermore, any photo can be infinitely enlarged, so the digital zoom capability has no relevance when choosing a camera.
What is hybrid Zoom?
Hybrid zoom is a combination of optical zoom and digital zoom. A 100x zoom can result from a 10x optical zoom lens plus a 10x digital zoom.
This combination allows you to achieve a very large focal length even for taking photos of the moon, but without damaging the image as much as a pure 100x digital zoom.
What is lens aperture? Understanding the f/number
The lens aperture influences the amount of light that reaches the image sensor. It is expressed in a f/number and results from a mathematical calculation with the focal length of the lens and the diameter of the diaphragm. As this is a fraction, the smaller the number after f/, the larger the aperture.
Advanced cell phones have lenses with larger apertures, such as f/1.8, f/1.6 or even f/1.4, which allow you to capture details in dimly lit environments. If the aperture were smaller (f/2.4, for example), the sensor would compensate for the lack of light by increasing the ISO or reducing the shutter speed, causing noise or blur in the photo.
However, the larger the lens aperture, the shallower the depth of field. This means that the lens can focus on a smaller area of the image, which makes background blur easier, but can harm sharpness. Therefore, a larger aperture is generally better, but it does not guarantee the quality of the camera.
What is the difference between digital, optical and on-sensor image stabilization?
Digital or electronic stabilization is done by software, while optical and sensor-shift stabilization consists of physically moving the camera components to compensate for natural hand shake, avoiding image blur.
Our article shows the differences between the types of stabilization in phone cameras. Digital stabilization is good for videos and is even used in action cameras, such as GoPro, in conjunction with more advanced algorithms. Mechanical stabilization (optical and sensor-shift) is more effective in photos.
Mechanical stabilization costs more and is not usually found in all cell phone cameras. In general, they are only on the camera with optical zoom, which would generate a more pronounced blur in the image if there was no stabilization. Furthermore, on-sensor stabilization is still rare on smartphones.
What is the image processor for?
The image signal processor (ISP) is responsible for interpreting the data captured by the sensor and transforming it into a digital image. It’s not the first component you’d think of when choosing a camera, but it’s gaining importance in phones, especially with the advancement of computational photography.
Modern ISPs do more than just convert raw data into photos. They also balance colours, reduce noise, improve details, and process features like night mode and portrait mode.
Apple’s Deep Fusion, for example, processes up to nine photos with machine learning algorithms to optimize texture, detail and noise in each region of the image. The Photonic Engine, launched on the iPhone 14, works with the ISP at an earlier stage, with uncompressed images, meaning it requires even greater processing capacity.
So isn’t it better to buy a professional camera instead of a cell phone?
Not necessarily. Professional cameras, such as DSLRs and mirrorless cameras, tend to have better specifications. They generally have larger sensors, which generate superior photos in low light, and have a wider range of interchangeable lenses available, including large apertures or high optical zoom capabilities.
However, smartphones are more portable and always at hand, which can be a big advantage if you want to capture a spontaneous moment. Additionally, the quality of smartphone cameras has improved significantly in recent years, particularly with the advancement of computational photography and more powerful ISPs.
Therefore, the best camera is the one that suits your needs and is available when you need it. For more details, see our article on the differences between smartphones and professional cameras.