What is an aperture and how does it affect the quality of images?

It is likely that many of you use your smartphone as a camera. Even those who have a SLR camera will not argue with the convenience of having a good compact camera in your pocket. The quality of the images taken by the flagship smartphones is more than enough to capture most everyday moments. Meanwhile, manufacturers are not stopping.

In addition to the trend of dual and then triple cameras, the last few generations of smartphones also offer cameras with a wider camera aperture. But what is an aperture or aperture? Let's find out.

Smartphones with an aperture of f / 1.8 and higher have become not so rare, although this parameter was previously considered solid even for professional-level lenses. The Pixel 4, Huawei Mate 30 Pro, and iPhone 11 all boast this type of aperture. Yes, it sounds impressive in the specs, but does this parameter really improve the quality of the images so much?

What is an aperture: light solves everything

In general, photography is based on getting the right amount of light, and a good rule of thumb for evaluating the quality of a camera is to find out how well it captures light. A first-class sensor paired with a flawless lens is the perfect combination for a DSLR SLR camera, but the same can be said for smartphones.

The small form factor of the smartphone means that the lenses and sensors are smaller in size, so less light reaches them, and this affects the final image quality. Smartphone manufacturers quite often began to use sensors with large pixel sizes (from 1.2 microns to 1.55 microns) to improve the shooting results. An equally important point is to understand how much light passes through the lens to reach those very pixels. And this is where the diaphragm works.

Let's deal with the f-stops well, so what is the aperture or aperture? The aperture is determined by the size of the hole through which light can enter the camera. It is measured in f-numbers or so-called f-stops, which are the ratio of the focal length divided by the size of the hole. Thus, the smaller the f-number, the wider the hole and therefore more light can reach the sensor, resulting in better lighting and less noise. If you narrow the aperture to full stop - (d / 2 to d / 2.8, d / 4 to d/5.8, etc. d.) - you will reduce the light collection area by half.

This has the advantage of reducing the exposure time required for a given amount of light. The result is reduced blurring when shooting in motion or from shaking hands, which, in combination with OIS, significantly improves the results. So, if you want to capture the perfect still frame, a wider aperture will help you achieve this.

The smartphone's cameras are located very close to the lens, much closer than in DSLRs. The focus of the camera is where the light from the lens converges on the sensor, and, accordingly, smartphone cameras have shorter focal lengths than conventional cameras. Since we know that the aperture value is the focal length divided by the hole size, it becomes clear why phone cameras have a wider aperture than most DSLR lenses, even though they don't necessarily capture light better.

Speaking of lenses, photography enthusiasts often associate a wider aperture with a lower depth of field, which allows for a nice soft bokeh effect. However, in the case of smartphones, we have a fixed aperture, a smaller sensor located close to the lens, and a wide enough viewing angle, so the depth of field of a phone camera will never be so small.

The smartphone's f/ 2.2 camera actually only provides a depth of field equivalent to the f/13 or f/14 aperture on a SLR camera, resulting in only a small amount of blurring. Modern phones with improved bokeh effects actually rely on software, not the aperture.

Although a wide aperture is not yet a guarantee of camera quality, a smaller aperture value provides more light for the sensor, which reduces the shutter response time to reduce blurring and reduces noise.

This value should always be considered in conjunction with the size in pixels, since larger pixels do not necessarily require a wider aperture to capture enough light. However, small pixels and a small aperture are a sure sign that you will have problems in low light conditions.

Lens Quality: where do the distortions come from

An equally important but often overlooked component of a smartphone camera is the lens, and like everything else, it can vary in quality. After all, you've probably noticed that a dirty lens takes bad pictures. It follows that a lens glass with poor clarity or transparency reduces the amount of light that hits the sensor, and therefore degrades the image quality.

Smartphones that use a very wide aperture require special attention to the design of the lens to avoid distortion, aberration and glare, which are not so rare. Agree, it is much more difficult to accurately focus the light when it passes through a wider hole, so when making lenses, you need to be as careful as possible.

< /p>Aberration distortion leads to a number of problems that occur when the lens cannot accurately focus light. Phones with a wide aperture are by definition less focused on a particular part of the scene than phones with a narrow aperture, and are therefore more prone to problems.Aberration distortion can be different: spherical aberration (reduced sharpness and sharpness), coma (blurring or distortion), field curvature (loss of focus at the edges), distortion (convexity or concavity of the image), and chromatic aberration (unfocused colors and divided white light).

Camera lenses, including those in smartphones, consist of several " correction groupsĀ», designed to focus light correctly and reduce aberration. Cheaper lenses tend to have fewer groups and are therefore more problematic. Lens materials also play an important role: higher quality glass and multiple coatings provide better correction and less distortion. Photographers sometimes call them "fast" lenses.

The quality of the lens is difficult to judge by the numbers or specifications, plus, many phone manufacturers do not even mention it. Unfortunately, the poor quality of the lenses makes reasoning about the aperture and pixel size useless, as it affects everything. But in the smartphone market, now there are well-known companies-manufacturers of optics, including Zeiss, Leica and others - and this is a huge plus.

In conclusion, it is worth saying that the quality of the lenses is no less important than other factors, but it is difficult to assess it without testing the camera.

Bottom line, as you probably already realized, the diaphragm is not everything. As in most areas of photography, when making a decision about buying a smartphone, it will not be the determining parameter, since in itself it is not an indicator of quality. However, it offers a number of advantages, including the ability to capture frames better in low light and a higher shutter speed.

For creative photography fans, a wider aperture will not give anything special in terms of interesting features, in addition to the chances of better images. As you understand, the lenses are fixed in the smartphone, and the small size of the sensors means that you will never see as much detail and get the kind of blur that you need for a perfect portrait. Currently, most smartphone cameras that offer bokeh effects do so using software and / or a second camera. Wide-angle and zoom cameras are more interesting options for such shots.

At the same time, small smartphone sensors are still sensitive to low light, and a wider aperture, combined with an excellent lens and sensor, helps to reduce noise and improve image quality.