As much as the technology behind smartphone cameras keeps improving, not all cameras are made the same. Some cameras offer better performance in low light while others promise higher resolution for picture clarity.

If you’re new to smartphone photography and/or are looking to invest in a phone mainly because of the performance of the camera, it can be a pretty difficult and overwhelming decision to make because of the sheer number of options available.

However, there are several things that you need to look out for that separate a good phone camera from a not so good one. In this article, we’re going to look at seven of them. Hopefully, this will help you make a decision that’s right for you.

And even if you’re not looking to buy a new phone, it’s nice to know what makes a phone camera good.

So, let’s get right to it.

1. Sensor

This is probably, if not definitely, the main contributing factor of picture quality in any digital camera, not just smartphones. It’s also one of the main reasons why smartphone cameras lag behind the more traditional cameras in terms of picture quality.

The sensor is basically a device that is made up of light-sensitive photosites (also called pixels) that capture light photons as they enter the camera. The camera’s image processor takes this light information from the sensor and uses it to recreate an image of the scene.

That’s a really simplified explanation of how it works. If you’re interested in knowing more, I’ve put together a more detailed (yet simple to understand) explanation of how phone camera sensors work. Be sure to check it out.

Size is really important when it comes to sensors. A big sensor means it can pack a lot of small pixels or accommodate fewer but bigger pixels. Each of these options has its own advantages, which I’ll touch on later.

Compared to a “normal” camera’s sensor, smartphones have incredibly small sensors. A full-frame DSLR sensor is 35mm in size. To date, the biggest smartphone camera sensor is a 1-inch type sensor, which is about the same size as that of an entry-level point-and-shoot camera.

The size of the sensor on smartphone cameras is expressed in fractions of an inch. Different cameras have different sensor sizes. A good phone camera will have a sensor that is very close to a full inch.

The smaller the sensor, the more compromised the picture quality is likely to be. Things like digital noise start becoming an issue, especially in conditions with poor lighting. Also, the resolution might be lower, which means you’re likely to lose detail in your images.

2. Pixel size

As already mentioned, the pixels (or photosites) on a sensor are the ones responsible for capturing the light that enters the camera. They can be likened to buckets that catch raindrops in the rain. The bigger the bucket, the more water it will catch.

The same applies to pixels, but instead of rain, they catch the light. The bigger the pixels the more light can be captured by the sensor. This results in well-exposed images, even in situations where the lighting is poor.

A good phone camera will not only have a sizeable sensor, but it will also have fairly large pixels. This is especially important in camera phone sensors because of how small everything is. If the pixels are too small, the images will be plagued with apparent digital noise.

Let’s go back to the rain and bucket analogy. If we put a big bucket out in the rain and then put a much smaller one right next to it, they will both gather as much water as they can hold, albeit the smaller bucket will hold far less water compared to the big one.

What’s inevitable from catching rainwater in a bucket is that you’ll end up with some dirt at the bottom of the bucket. In a big bucket, this is not a big deal. However, in the small bucket, this dirt is very noticeable.

This is similar to problem from which a bad phone camera with tiny pixels will suffer. Because a smartphone camera is a digital device, it generates heat and noise just like any electronic device.

If the light-receiving buckets of the sensor (pixels/photosites) are not big enough to receive a lot of light, then the noise from the electronics of the camera will be very visible.

The size of the pixels on the sensor is measured in micrometres/microns and expressed using the symbol ‘µm’ or just ‘µ’. One thousand micrometres equals 1 millimetre.

In 2020, the largest pixel size on smartphone camera sensors is 2.4µm, found on the Huawei P40 Pro. Interesting, the P30 Pro has smaller pixels (0.8µm). However, like many smartphone cameras with high megapixel counts, it uses pixel binning.

Pixel binning allows neighbouring pixels on a sensor to be merged together to create larger pixels. For example. The Samsung Galaxy S20 Ultra can increase the size of its pixels from 0.8µm to 2.2µm after pixel binning.

If a phone camera has a very tiny sensor and very small pixels, chances are the resulting images will be of poor quality.

3. Megapixels (Resolution)

The surface of the sensor is made up of many pixels. The total number of these pixels is referred to as megapixels. Mega- is a prefix that means ‘of one million’. So, if a camera is said to be 12MP, that means it has 12 million pixels that capture light to produce an image.

In simple terms, this means that the image could be 4000 pixels wide by 3000 pixels high. This is known as the resolution.

The megapixel count of a camera is the source of much confusion, especially amongst the layman consumer and hobbyist photographer. Because smartphone companies base the marketing of their mobile cameras mostly on the number of megapixels they have, a lot of people believe that more is better. There is some merit to that but that’s not entirely true. (You can find out the real truth here.)

The resolution or detail of an image is determined by the number of megapixels of the camera. A picture taken with a 5MP camera will not have as much detail as one taken with a 20MP camera.

So the more megapixels a camera has, the higher the resolution of the images it will produce. This is important if you want to print your mobile photos, especially in very large sizes.

While this is true, packing the sensor with a ton of pixels comes at a sacrifice– the pixel size. As previously mentioned, large pixels are ideal because they’re able to capture more light and perform well under low lighting.

Because smartphone camera sensors are so small, it would make sense to try to fit them with pixels that are big enough to capture as much light as possible, but not too few to the point of losing a lot of resolution.

As mentioned earlier, some phones such as the Samsung Galaxy S20 Ultra have a 108MP primary rear camera. In my honest opinion, I don’t think cameras need that many megapixels. That’s why they use pixel binning by default. It makes more sense to have larger pixels than an unnecessarily high number of megapixels.

Unless you want to print large sizes of your smartphone images onto posters and such, there really is no need for anything above 16MP. Even that is generous. An 8MP smartphone camera is enough for everyday mobile photography.

A decent mobile camera will strike a good balance between the number of megapixels it has and the size of each pixel. Again, this also depends on the size of the sensor itself.

4. Aperture

Aperture refers to the diameter of the opening through which light enters the camera. It works in pretty much the same way as the iris in our eyes, which expand or contract to regulate how much light hits the photoreceptors at the back of the eye.

Similarly, traditional lenses for normal cameras have a mechanical diaphragm that controls how much light enters the camera and hits the sensor. On the barrel of a typical lens, there’s a ring that you can turn to adjust the size of the aperture.

How dark or bright the image will be is determined by the size of this opening which is expressed in f-stops. The smaller the f-stop number, the wider the opening, and therefore, the more light reaches the sensor.

Aperture can be adjusted on traditional camera lenses but phone camera aperture works differently— it’s fixed. This means that if a smartphone is said to have an f/2.2 aperture, then that is that. You cannot change it to allow in more light or less light by adjusting the aperture.

This may sound limiting (and it is) but due to size, smartphone cameras need their aperture to be as wide open as possible in order to allow enough light to reach the tiny sensor.

If you’re looking to buy a phone based on the camera specs, look for one with a really wide aperture. The current leader in aperture size is the Honor 20 Pro, which has an aperture of f/1.4, the widest of any smartphone camera. Other phones are not too far off.

Variable aperture on the Samsung Galaxy S9. The image on the left shows the aperture set to f/1.5 and the image on the right shows the aperture at f/2.4.

Samsung’s flagship Galaxy S-series phones are known to have an aperture of f/1.5. Starting with the Galaxy S9, they’ve taken things further and introduced something not seen on any other mobile camera.

Their cameras have a variable aperture which sees them switch between f/1.5 and f/2.4. However, this feature was dropped in the Galaxy S20 series, which is unfortunate.

5. Lenses

Unlike lenses for traditional cameras, smartphone camera lenses are made of plastic, not glass. That being said, their quality can be quite good.

However, camera lens quality differs from phone to phone and can substantially affect picture quality. A poor quality lens is not as sharp as a good quality lens and may struggle with image issues such as chromatic aberration.

So how do you know if a phone has good quality lenses? You don’t– at least not from the mobile camera specs made available publicly. What I have found is that smartphone manufacturers don’t usually mention the specific quality of their lenses unless they have partnered with a well-known brand such as Leica or Zeiss. Instead, their focus is on aperture and focal length, both of which are important to know, too.

One way to know the quality of the lens, and probably the best way, is to look at reviews posted online. Websites like GSM Arena and DXOMARK run tests on mobile cameras and post their results online. From there you can get an idea of how the lenses perform and if they have any imaging issues.

And as already mentioned, partnering with a known lens brand is another way to assure lens quality. But that’s not to say that phones without known lens brand partnerships don’t have good lenses.

For example, phones from Apple and Samsung don’t have branded lenses on their cameras yet they produce some of the best mobile photos. In a way, they themselves as brands are sort of an indication of quality. So, the reputation of a phone brand when it comes to imaging can be used as an indication of lens quality.

6. Image stabilisation

It’s been said that camera shake is the thief of sharpness. That’s very true. When taking photos with any camera, the slightest camera movement can result in blurry shots. And if you’re working with a slow shutter speed, the worse the blur will be.

That’s where image stabilisation comes in. As the name suggests, the aim of it is to keep the image stable in order to keep the image sharp.

When you hold your phone to take a picture, it is inevitable that your hands will move, even if just slightly, mainly due to the phone’s lack of ergonomics for photography (unless you attach a specialised hand grip).

A phone that has optical image stabilisation (OIS) is better equipped to deal with this sort of issue. In basic terms, this is achieved by using a floating lens that is attached to two gyroscopes and small motors.

Whenever movement is detected, these elements are moved by a microcontroller to counteract the motion of the camera. This is actually very similar to how a stabiliser minimizes camera shake whenever there’s any movement.

A good phone camera should have OIS as it will make capturing sharp images easier for you. By countering the camera movements caused by shaky hands, the lens is able to stay in one position and therefore produce a sharp image despite the fact.

However, OIS cannot prevent blur if the subject moves around or if the camera shake is more than what it can handle. For that, you’ll have to get the subject to remain still if possible or use a camera support system such as a tripod.

7. File format (RAW)

When taking a photo with your phone, the image is usually processed and compressed, and then saved to your mobile as a jpeg file. Although this may work just fine for the average user, it might not be the best option for someone who wants to do more with their mobile photos.

This is because when a picture is saved as a jpeg, it loses some detail and quality due to compression. This renders the image less flexible when it comes to editing because some data would have been discarded.

The solution? Shoot RAW. Unlike with a jpeg image, a RAW file is uncompressed and unedited. In other words, the camera won’t apply its own contrast, white balance, sharpness, etc. to the saved image. Instead, the raw image data is saved to the phone’s storage.

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