If you’re into smartphone photography, one spec you’re probably looking at is the megapixel count of a smartphone camera. But is it really a reliable indication of image quality?
If you look at DSLRs and mirrorless cameras and compare them to smartphones, you’ll find that some entry-level and mid-range phones have higher pixel counts. But they still have poorer image quality compared to them.
So, let’s take a look and see which is more important: the number of pixels or the size of the sensor.
How Camera Sensors Work
Before diving into the subject, we must first understand what camera sensors are and how they work. A digital camera must convert light into electrical signals when taking a photo. It does this by using the lens to focus light onto an image sensor.
However, the image sensor is not just a single light sensor. Instead, it’s made up of many smaller light sensors called pixels. Each pixel measures the amount of light it receives and converts it into a signal. The camera’s on-board computer then captures the signal from each pixel and constructs an image of it.
There’s more than what’s written above, but that’s the gist of how digital cameras take pictures. If you want to know more, you can check out our primer on how imaging sensors work.
Does megapixel count really matter?
Since individual pixels capture light, many would argue that megapixels are important. And that’s true up to a point. After all, the print size of an image will depend on its number of pixels. For example, at the ideal resolution of 300 pixels per inch, you can only print an 8 x 10 inch image from an 8 MP photo before it starts to blur.
However, in today’s age when most of our photos are usually stored and shared on our phones, having a 64 MP camera on a smartphone is overkill. Canon’s flagship mirrorless and SLR cameras only have 24 and 20 megapixels, respectively. Even Hasselblad’s professional medium format cameras only display 50 megapixels.
The Effect of Sensor Size on Images
You have to remember that pixels have to live inside a sensor. So if you cram 108 million pixels into a 1/1.33″ sensor, those pixels must be exceptionally small. When you reduce the size of your pixels, you also reduce the amount of light it picks up. This reduction will have an impact on the final result of your image.Here are its possible effects:
1. Increased noise
When you reduce the amount of light captured by a given pixel, it increases the signal-to-noise ratio of that individual pixel. Indeed, there will always be noise, and you can only overcome it by filling the sensor with actual light signals. But if your camera uses small pixels (packing as many pixels as possible into a small sensor package), there won’t be as much light data to overcome the noise already there.
2. Low light performance
When shooting in dark areas, a camera with a smaller sensor will be at a disadvantage. Smaller sensors will capture less light for a given exposure time. So to make sure it can capture what you see, the camera will either use more power to raise its ISO (thus increasing noise) or lower shutter speed to gather more light (meaning you must have a tripod or a very stable camera hands).
3. Depth of field
Smaller sensors usually have large depths of field. This is because a smaller sensor will also capture a smaller area. So, if you want to photograph a flower, you will have to take a step back to capture it in its entirety.
However, a camera with a larger sensor captures a larger area. So if you want to fill your camera frame with the flower, you will either have to get closer to the flower or use a lens with a longer focal length. When you do this, you get a shallower depth of field in your image, making your subject stand out from the background.
4. Smaller field of vision
When you have a smaller sensor, you also get a lesser viewing angle. So if you want to capture a wide scene but have a smaller sensor, you will need to use a wider lens. However, a wider lens can introduce distortion, such as the fish-eye effect.
5. A more affordable and lighter system
Perhaps the only advantage of a smaller camera sensor over a larger one is price and size. Since smaller sensors consume less power and require fewer resources to produce, they are generally more affordable than larger image sensors.
Additionally, the smaller sensors are physically smaller than their larger counterparts, allowing them to be placed in thinner devices, like smartphones, without the need for massive camera bumps. They also need smaller diameter lenses, so you don’t need massive holes in the back of your phone if you have a smaller sensor.
Image processing matters too
Despite the drawbacks, smartphone makers are still striving to add as many pixels as possible to their cameras. But aside from looking impressive on paper, smartphone makers want to add more pixels to their smartphones to take advantage of computational photography.
Smartphones can overcome many of these limitations by using powerful chips and AI. That’s why today’s phones have great imaging performance, even though they have small camera sensors.
For example, the Google Pixel 6 and Apple iPhone 13 Pro Max can produce some of the best images today. Their output is usually clean and noise-free; even their night shots are crisp and clear. And while the artificial bokeh on these devices isn’t as good as the real thing, they’re getting better with each generation.
Still, you’ll find that the trend for smartphone cameras is larger sensor sizes. You’ll notice it on the iPhone: the iPhone 11 Pro Max has a pixel size of 1.4µm, while the iPhone 12 Pro Max sports a 1.7µm pixel sensor. The iPhone 13 Pro Max has an even larger pixel size of 1.9µm, making it arguably one of the best camera phones around today.
Don’t let the megapixel count fool you
Many phone manufacturers use pixel count to impress potential buyers. However, they are really not a good indication of quality. After all, you can find entry-level smartphones with 48MP rear cameras that produce terrible images.
Many manufacturers add numbers and other jargon to look cool or advanced, so it’s best you know which specs to look out for and which to ignore. But if you’re buying a smartphone for its image quality, the best thing to do is check reviews and actual image samples before making a choice.