Camera comparison: the 12MP iPhone 6s vs the 16MP Galaxy S6, or why megapixels aren't all that matters in a camera
There are many technical specs and features that can be associated with a digital camera – its aperture, focal length, pixel and sensor size, auto-focusing tech, lack or presence of image stabilization, and the list goes on and on. Having these into account, an experienced photographer should be able to determine whether a given camera setup suits their needs. To the average consumer, however, a camera's megapixel count is still the figure that most strongly correlates with image quality. The more megapixels a camera has, the better the images it produces, or at least that's the general assumption consumers still hold on to. But in actuality, the matter is a tad more complicated.
We're not saying that megapixels and their number don't matter. Of course they do. But judging a camera's potential solely by its megapixel count can be misleading. An ideal example of that would be a comparison between the iPhone 6s and the Samsung Galaxy S6. The former has a 12MP camera, while the latter has a 16MP one. That's 33% more pixels packed inside the Galaxy S6's sensor, meaning that its photos should be noticeably more detailed than the iPhone's, right? Well, not necessarily.
Getting the full picture
A variable that rarely gets mentioned in a smartphone's camera specs is the sensor's native aspect ratio. That's the proportional relationship between the width and the height of the pixel array of the image sensor – the iPhone's camera shoots 12MP photos at 4032 by 3024 pixels for an aspect ratio of 4:3, while the Galaxy S6 takes 16MP images at 5312 by 2988 pixels, which equates to an aspect ratio of 16:9. Here's how these figures and proportions look when visualized:
As it becomes clear from the graphic above, the cameras on the iPhone 6s and the Galaxy S6 shouldn't be all that different when it comes to resolution and image detail. Yes, the Galaxy S6 does have an advantage of 4 megapixels over the iPhone 6s, but these are taken up by the additional width of the frame. The height of the images produced by the two phones is nearly identical, standing at about 3000 pixels. In other words, the extra pixels that the Galaxy S6 has at its disposal produce a wider image, not necessarily a more detailed one, and if we were to take identical crops of images produced by the two phones' cameras, they should look very, very similar at 100% zoom.
But the rabbit hole goes even deeper
The visualization above isn't perfect, as we haven't taken the two cameras' focal lengths into account. Focal length, expressed in millimeters (mm), goes hand in hand with the horizontal and vertical viewing angles of the camera – a smaller focal length translates to a wider viewing angle and vice versa. But to keep things simple, we've chosen to ignore this variable as it makes a very small difference in our case. The iPhone 6s and Galaxy S6's cameras have focal lengths of 29mm and 28mm respectively.
Another factor that we've skipped is that the two sensors pick up different areas of all the light entering the sensor. To get a better understanding of what we mean, take a look at the graphic below. The black circle represents the area illuminated by the light entering the camera. Note that the area has a circular shape because the camera's lenses are, you know, circular. But the image sensor is a rectangle. It produces rectangular images that we view on rectangular screens. This brings us back to aspect ratio and how it affects images. In our particular case, the Galaxy S6 produces wider images, while the iPhone 6s has a wider vertical field of view, all because of the difference in aspect ratios between the two sensors.
A look at real-life photo samples
Now seems like a fine time to leave theory aside and have a look at some real-life photo samples. In the slideshow below you'll see three pairs of images taken with the iPhone 6s and the Galaxy S6 under identical conditions. In addition to the full-resolution images, we've also included crops at 100% zoom to demonstrate that there's barely any difference in the amount of detail captured by the two cameras. And when there is, it is caused by the two cameras' sharpening and image processing algorithms, not by the difference in megapixel count. At the same time, the full-resolution images demonstrate the difference in the two cameras' horizontal and vertical angles of view caused by their differing aspect ratios – the phenomenon we highlighted above. Feel free to zoom in on those to explore and compare the quality of details captured by the two cameras.
Please note that the slideshow contains full-resolution images that might take a while to load.
Megapixels are not all that matters in a camera – that's the one thing we hope you'll walk away with after reading this article. Clearly, in the case with the iPhone 6s and the Galaxy S6, the latter's 33% higher megapixel count does not result in a dramatic difference in detail quality. There's barely any difference at all, as the above photos confirm, and when there is, it is because other factors come into play, not because one camera has more megapixels than the other. This serves as a reminder that cameras are complex systems. Assessing two cameras' qualities by comparing a single specification could be misleading and plain wrong, regardless of what a sales representative or a company's marketing department wants you to believe. At the end of the day, the best method to tell if one camera is really better than another remains a comparison between the images produced by the two. And trusting what your eyes like better, of course, instead of weighing figures side by side.