Today, good smartphone cameras can compete with their big siblings, the digital cameras. TECHBOOK reveals which technical details you should pay attention to with the cell phone camera and which terms you should know.
Our mobile phones are our constant companions in everyday life. We use them to communicate, look for suitable train connections, find out about current events – and above all take photos. For many, a good smartphone camera is now one of the most important criteria when buying a cell phone. But what exactly should you pay attention to? TECHBOOK explains what makes a good smartphone camera and what it should be able to do.
This is how a smartphone camera works
A smartphone camera works like a “real” photo camera. The light first falls through the lens, which consists of several differently shaped lenses and an aperture. So the lens regulates the incidence of light before it reaches the sensor. The image sensor acts as a “retina”, converting the incoming light into electrical charge and absorbs brightness and colors. In the end, the sensor converts the analog information – the light – into digital information, which can then be seen as a finished image on the smartphone. On the path that the light takes, various components of the camera and not least the software are decisive for what the end result looks like. Some elements are more relevant than others.
The sensor as the heart
A comparatively large sensor is installed in the mobile phones with the most powerful photos these days. On the one hand, this prevents color noise (more on this in the next paragraph), and on the other hand, less electrical voltage is required for ideal image exposure. With the automatic shutter speed, the aperture is not closed mechanically, as with a photo camera, and the light is thus passed on. Instead, the sensor is simply activated for a brief moment, which makes extremely short exposure times possible. This saves electrical charge and thus prevents image noise.
Not all manufacturers have so far specified the sensor size of their smartphone cameras, but more and more companies are playing with open cards in this regard. When a size is listed, a minimum of about 1/2.5 inch is a good guide.
Pixels aren’t everything
One of the most prominent specifications that manufacturers make for their smartphone cameras are the megapixels. Many interpret this to mean that a camera with a particularly high number of megapixels automatically takes better pictures. However, that is not entirely true. For classification: A megapixel corresponds to 1,000,000 pixels. The pixels form the surface of the sensor and each consist of a micro lens, a color filter and other conductor tracks. Also, the number of pixels represents the resolution, so a high number means high resolution.
However, this advantage only comes into play in combination with the sensor size. If the sensor is small, but the resolution is very high, image noise quickly occurs. If, on the other hand, the same number of pixels is distributed over a larger sensor, the pixels themselves are automatically larger, can absorb more light and do not emit the primary color (red, green or blue) assigned to them to the neighboring pixels, which in turn is the case prevents unsightly color noise in the photo.
It is therefore definitely worth paying attention to the number of megapixels. However, the number is only completely meaningful if the sensor size is also known, and in this regard the manufacturers unfortunately often keep a low profile. As a guideline, you can still assume a minimum of 8 to 12 megapixels. This size is sufficient to be able to print out a photo in good quality and DIN A4 size.
More on the subject: Why more megapixels don’t always mean better pictures
The trend is towards multiple lenses
Of course, the lens is also an important component on the way to a good-quality mobile phone photo. Before the light can even reach the sensor, it must first pass through the lens. The current trend in smartphones is towards a multi-lens system; so more than one lens is installed. On the one hand, this is practical because it allows more diverse angles to be taken when taking pictures, simply by installing both an ultra-wide-angle lens for wide-ranging landscape shots and a telephoto lens for close-up shots.
On the other hand, the functions become more diverse without the entire housing having to grow with it. This applies to the zoom, for example, which can be used without any major loss of quality due to the different focal lengths of the lenses. Of course, there are also excellent smartphone cameras with just one lens, but the advantages of a multi-lens system cannot be denied. If you like using your phone to zoom in on objects and want to take comprehensive ultra-wide-angle shots in the next breath, you should pay attention to the built-in lenses of your phone camera.
Aperture – more is more
Although the aperture is part of the lens, it should be treated separately here because of its importance. The size of the aperture determines how much light ultimately reaches the sensor. The well-known information such as “f/1.8” defines the relationship between the focal length (=f) and the given width of the aperture. Therefore, the lower the value, the larger the aperture. A large aperture allows better shots in low light and also shortens the exposure time and thus the risk of taking a blurred photo. The so-called bokeh effect, in which the background sharpness is lower and the focused object is emphasized in the foreground, works better with a large aperture because the drawing of the blurred area is softer. For most smartphones, the aperture size is preset and cannot be changed; the key figure is all the more important when making a purchase.
Current top models such as the iPhone 11 Pro usually have an aperture of f/1.8, which can be used to create well-exposed photos even in poor light. For example, the Xiaomi Mi Note 10 has an aperture of f/1.69, the Samsung Galaxy S10 (Plus) even f/1.5. Especially in portrait. And for night shots, a large aperture is important. If you tend to take snapshots and landscape shots with your cell phone, this value is less relevant to you.
Image stabilizer ensures a significant leap in quality
The image stabilizer of the smartphone camera is also playing an increasingly important role. Especially with mobile phone recordings, there are often blurred pictures because we usually use the camera without a tripod, but simply take pictures freehand. That’s why many current smartphone cameras offer an image stabilizer that compensates for shaking to a certain extent. The optical image stabilizer, which gives the lens a little room to move, is particularly effective. It is then not locked into a rigid position and can compensate for small stutters with a position sensor. The optical image stabilizer is now part of the standard equipment for the flagships. In the mid-range, if you care a lot about quality, you should also make sure the option is there.
Software – Optical vs. Digital
In addition to all the built-in hardware, the software is of course also important for the smartphone camera. This can compensate for any deficiencies in the rest of the equipment. In general, solutions built into the hardware usually work more effectively than digital software solutions.
However, this also makes the camera and thus the smartphone bigger and heavier, which is why in many cases the functions are transferred to the software. Examples are the zoom function and the image stabilizer just mentioned. Both can be implemented optically by installing additional (movable) lenses. In both cases, however, the software can also intervene to correct it. With the stabilizer, the image is first zoomed in so that slight camera shake can be compensated for by shifting the corresponding photo section. However, part of the resolution is also lost in the process. The same applies to the zoom: the digital software-based variant enlarges the existing image section and thus causes a lower pixel density or resolution. Optical zoom changes the optical proximity to the lens using the lens.
Nevertheless, camera software offers many extensions that can be very useful for the passionate smartphone photographer. Night mode, manual white balance, various filters, panorama mode, a possibly built-in photo AI that recognizes motifs and much more. It is therefore worth finding out about the possible functions of the software in advance and setting priorities if necessary. And when in doubt, even the best hardware equipment is of no use if the software cannot keep up.
Conclusion
If you want to be thorough when buying a smartphone or pay particular attention to the camera performance, you should keep several aspects in mind. The purpose is decisive: What is the main motive? The pixel density (min. 8 megapixels) in combination with the sensor size (min. 1/2.5 inch) is generally important. Different built-in lenses and an optical image stabilizer are less important for the quality, but crucial for a nice photographic experience. If there is a lot of filming, this aspect should be given greater importance. A moving picture can have a sliding effect for the viewer if a good image stabilizer is installed.
It’s also worth taking a closer look at the camera’s software: what functions are there and where are any hardware defects corrected? A variable aperture (several lenses) is preferable if you want to be as flexible as possible when choosing a subject. The largest possible aperture (min. f/1.8) is a good guideline, especially for portraits or photos with little light. A small aperture and thus a high f value (f/4) is better for capturing landscape shots. Depending on the needs, more or less importance should be attached to one aspect.