My Sony has 61 million pixels. I could buy a Fuji with 100 million pixels. I could even buy a Samsung phone with 200 million pixels. All of this sounds very impressive until you realise that 99% of us never need that many pixels 99% of the time.
The reason these high megapixel counts sound impressive is not because they are, it’s because well paid people in marketing departments tell us they are.
Let’s go back to that phone for a minute. Let’s also assume I know nothing about photography – yes, I hear the catcalls from one or two of you. However, I want a phone that takes good pictures; I have a keen eye, and I want better quality. I know nothing of pixel size or pixel density; I just want the highest resolution possible, and I don’t know why.
So in the phone store, a salesman who is equally clueless about megapixels as me tells me the iPhone has 48mp and the Samsung has 200mp. Which am I going to buy?
I will allow a gimme for the Fuji 100mp and indeed Hasselblad equivalents because they are being bought, in general, by people who really do know about pixels. However, when it comes to smartphones and lower-end mirrorless cameras, do we really need those immense resolutions?
All Pixels Are Equal But Some Are More Equal Than Others
Let’s go back to that iPhone, it has 48mp. That sounds reasonable, yet many modern mirrorless cameras have significantly less. So why would a dedicated photographic tool have fewer pixels than a smartphone? It comes down to two key factors that newcomers to photography are rarely told about.
First, the size of the pixel. Let’s use a car analogy: faster cars often have bigger tyres. This is because it allows the handling to match the performance of the car. Bigger is better. In photography, the bigger the pixel, the more light it can absorb and hence the better the image quality. However, that’s not the full story.
Going back to our car analogy, if the tyres (wheels) are placed too close together, the car is going to handle terribly. The same is true of our pixels. Big pixels sound great, but if they are placed too close together, they start to reduce the image quality. Welcome to pixel density.
A high pixel density can introduce noise to an image as the ISO is increased. This is simply because our camera is amplifying the signals coming from the pixel to boost the amount of light recorded. The closer those pixels are, the more interference from each other they experience, and that manifests itself as noise.
Now, this is quite a simplistic look at it, as these days we have other factors that reduce noise such as stacked sensors and, in smartphones, night or low light modes. However, as a rule, the closer the pixels are together, the lower the image quality. This may not show up much in a shot taken in good light, but it will in less optimal lighting and definitely will in editing. Edit a 48mp iPhone image alongside, for example, a 50mp mirrorless camera image, and the mirrorless will have much more leeway.
The smartphone sensor is tiny compared to even a 1” sensor found on compact cameras; step up through Micro 4/3rs, APS-C, to Full Frame, and that difference in image quality becomes pronounced.
It’s Actually The End Result That Counts
So why is it that many people are very happy with 48mp or even 200mp output on their phones? Put simply, it’s because of where the image ends up. Most smartphone shots only ever end up on a screen. At the very best, that might be a full sized 4k monitor; more likely, however, it will actually be seen on the screen of the phone that took it.
Stepping up to bigger cameras and more experienced photographers, still, the vast majority of our work will be seen on screen. When we print, we would rarely go much bigger than 20×16 inches, and that’s 28mp if we print at the optimum 300 dpi. We can easily drop the dpi significantly and get even larger prints without any noticeable image quality drop.
Perhaps that’s why a lot of cameras have stayed in the 24-33mp range for quite a few years now. But it goes beyond that; having lower MP often gives us more dynamic range and a cleaner, more film-like image. A few months ago I compared my 61mp Sony a7Rv to my 8-year-old Fujifilm X-E3. I was astounded at how close the images looked in the real world.
A higher megapixel count becomes even less relevant when we put our images on social media. Even if we upload them at full resolution, they will be downsized to, at best, 2048 pixels and often a lot less. Add in all the compression used to make the images load quickly, and even 24mp would seem too much.
There are cases for high megapixel counts. High-end commercial work, for example. Sports and wildlife is another. Photographers can easily utilise those extra pixels to crop in on remote subjects and, in general photography just to give us more room in the crop.
However, those megapixels come at a cost. The file sizes are significantly larger; have you seen the price of storage recently? The processing power required to edit is also significantly increased, with much better-specced computer hardware. Plus of course the price of the high-megapixel cameras themselves; they don’t come cheap; megapixels mean money.
Of course, the marketing people already know that.
