Does more megapixels means better image quality or better camera?

November 3, 2015

sensor pixels

There are many different phone cameras out there. The sensor plays a significant role in determine the image quality. Image sensors are continuously being improved in each generation, featuring different sensor sizes and pixel count.

The higher the sensor resolution, the higher the image resolution is. In other words, sensors that feature more light-sensitive pixels, will result in a higher image resolution.  There are cons and pros of having a high resolution sensor, but it depends on other factors, not just the actual sensor resolution on its own.

Some people might think that if a mobile phone camera has 13MP, it might produce a better image quality than a 8MP camera – but is it true?

In lab  tests, the image quality is measured by evaluating sample images taken with the camera and rating various image quality parameters, including: color accuracy, texture (fine details), image noise, artifacts, dynamic range, exposure and contrast, etc. DxOMark is one of the websites that runs such tests. The site measures the image quality of mobile phone cameras for both photos and videos separately.  It’s one of the most reliable sources for mobile phone and digital camera image quality testing.

Let’s first take a look at the top mobile rating table. As of the time of writing the article, these are the top 5 leading camera phones:

  • Sony Xperia Z5 – 1/2.3″ 23 MP (1.12 micron pixels), 5520 х 4140 pixels
  • Samsung S6 Edge – 1/2.6″16 MP (1.12 micron pixels), 5132 x 2988 pixels pixels
  • Google Nexus 6P– 1/2.3″ 12.3MP (1.55 micron pixels), 4000 x 3000 pixels
  • Moto Droid Turbo 2 – 1/2.4″ 21MP (1.1 micron pixels), 5,344 × 4,008 pixels
  • LG G4 – 1/2.6″ 16MP (1.12 micron pixels), 5421 x 2948 pixels

The overall best image quality score goes to the Sony Xperia Z5, and although it has the highest combines score, the Galaxy S6 edge received a higher score in the photo category. We can see that the highest resolution sensors aren’t necessarily at the top.

There are various factors that affect the image quality, among those are the size of each photosite/pixel (large = more light gathering capability and more color data), the sensor architecture (CMOS vs BSI vs Stacked), the lens optics and aperture, the image processing, etc. So although you might see a mobile phone camera having very high resolution with the top score, it doesn’t mean that high resolution sensors perform better than lower resolution sensors. In fact, it usually works the other way around, because most mobile phone cameras have very small sensors, so using less pixels can allow bigger pixels. Bigger pixels means that the sensor can collect more color data and produce an image with better image quality.

If you compare a 5MP sensor from 5 years back versus a 10MP sensor, you can clearly see that the 10MP outperform it in almost any test. This is because sensor technologies have improved by a large margin, and this is one of the main reasons for the huge improvement we see in image quality and low-light performance.

Phone manufactures try to find the optimal balance between image quality, features and resolution. For example, if a mobile phone camera has an optical image stabilization, it can allow photographers to shoot in slower shutter speeds and have less need to shoot in relatively high ISO sensitivities. So that camera can have relatively smaller pixels and higher resolution and provide more detailed image with a lower impact on the low-light performance.

Google for example went with a relatively large sensor and lower resolution with its Nexus 6P. It features the lowest resolution among the five smartphones, but has the largest pixels. This means that there is less need for an optical image stabilization (which the 6P lacks), and it can provide a detailed image and excellent low-light performance at the same time.

Let admit it, not all of us need a 20MP camera. Most people share their images on social networks where the image is either cropped or viewed in lower resolution. Furthermore, those high resolution images weigh more in terms of their file size. You have the option to set the camera to shoot at a lower resolution. In most phones, the camera will use the entire sensor area and than crop the image, in more advanced configuration the camera will use “pixel oversampling” to combine the details of neighbour pixels to form a large “fat” pixel to improve the overall image quality.

So when you go shop for a new smartphone or tablet device, you need to make sure that you know as much as you can about the camera specs and features. Don’t just search for the phone with the highest resolution, because it tells very little about the image quality and camera performance in low-light.  Many of you probably won’t take advantage of that high resolution. I personally prefer a high resolution image because I like editing and cropping my photos, but if the image quality is below average I’ll obviously skip that phone. In fact, if the image quality is good, you can even digitally enlarge it and still get a very detailed enlargement. Some phones even have advanced digital zoom algorithms with minimum impact on image quality.

So to sum things up: more pixels doesn’t mean better image quality. You should find out more information about the camera lens, aperture, sensor technology, read reviews and view sample image comparisons to find out whether one camera can produce better quality images than the other.

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