It’s hard to compare apples to apples when you want to buy a camera. Product descriptions throw all these numbers at you, such as the number of megapixels and the sensor size, but you may not understand how each affects image quality. Plus, for interchangeable lens cameras, many people will tell you the lens is more important than the camera body.
It’s easy to get confused if you don’t understand how these factors are related. So, let’s talk about it. What matters most for image quality? The number of megapixels, the sensor size, or the lens you’re using?
Megapixels, sensor size, and the lens you choose all affect image quality in different ways. Megapixel count is important in certain types of photography, while sensor size affects the quality of each pixel. Better lenses improve the quality of the image by compensating for smaller photosites.
Read on to find out what megapixels are, how megapixels relate to the sensor size, and what effect the lens has on megapixels.
What Are Pixels in an Image?
First, what are these megapixels we’re talking about? A pixel is the tiniest individual piece of a digital image. Modern digital images are made up of millions of these tiny pixels.
For example, consider an image that is 5,472 pixels wide by 3,648 pixels tall. There are 19.9 million pixels in the image. These 19.9 million dots blend together to create a picture that our eyes translate as one seamless image.
What Are Megapixels in Cameras?
The megapixel count of a camera tells you how many pixels of information it is capable of capturing. One megapixel is equal to one million pixels in an image. Thus, a 16 MP camera can capture 16 million pixels of information.
The number of megapixels in cameras has grown exponentially in the last 20 years. In 1999, 3 MP cameras were seen as professional quality cameras. Now you can get a smartphone with a 64 MP camera.
However, many professional level cameras are still hovering around 20-30 megapixels. Though, of course, more and more are appearing in the 45-60 MP range. And let’s not even get started on the massive medium format cameras!
So why would you drop over $3,000 on a 61 MP Sony A7R IV, if you can spend a few hundred dollars on a smartphone with a higher megapixel count?
Because the megapixel count is not the end of the story.
You also have to consider the sensor size of the camera. Full-frame cameras have a sensor that is physically larger than crop sensor cameras, point-and-shoots, and smartphones.
The sensor is a photo-sensitive device that is capable of capturing light and color. But the sensor is not a smooth, flat surface. There are millions of tiny light-capturing cavities called “photosites” on the sensor. Each one of these cavities captures the information for one pixel.
One million pixels equals one megapixel. Thus, if you have a 16 MP camera, there are 16 million photosites on the sensor.
If those 16 million photosites are crammed onto a small sensor, each one of the sites has to be smaller to make them all fit. If the sensor is larger, the photosites can be larger, thus producing a better quality pixel.
Larger photosites can produce better quality images in low light and have a wider dynamic range. Thus, if you regularly shoot with a high ISO (perhaps ISO 6400 and higher) a higher MP camera won’t be as useful to you as one with fewer MP and larger, better quality photosites.
Do More Megapixels Mean Better Photo Quality?
Yes and no. Because of this interplay between megapixel count and photosite size, more megapixels doesn’t always mean better quality. More pixels are better, but the advantage is limited by the physical size of the sensor.
For example, a 16.2 MP Nikon D4S full-frame camera will do better in low light situations and produce a wider dynamic range than a 36.3 MP Nikon D810 though it also has a full-frame sensor.
Likewise, a full-frame camera will produce significantly better results than a smartphone, even if the smartphone has a higher megapixel count. The sensor in that smartphone cannot compete with the physical size of the 36mm x 24mm full-frame camera.
How Many Megapixels Do You Really Need?
At this point, you might be feeling even more confused. You might even be thinking, “just tell me how many megapixels I need!”
Unfortunately, the answer isn’t the same for every photographer.
If you plan on working in a field of photography where you will regularly be printing images, more megapixels will benefit you. For example, photographers who work in advertising or do food photography for cookbooks benefit from higher megapixel cameras.
When printing, there is a minimum number of pixels per inch (or dots per inch when printing) that you can print without the image starting to look pixelated. You can get an acceptable image by printing at 150 dots per inch (dpi). But for professional printing, you need a minimum of 300 dpi for a high-quality image.
Thus, in order to create high-quality printed images, you’ll want a higher megapixel camera. This also gives you a bit of wiggle room to crop images in post-production.
On the flip side, if you primarily photograph weddings, the better low-light capabilities of a camera with fewer megapixels will serve you more.
What Is More Important: Megapixels or Lens?
There is another piece to this puzzle in the search for amazing image quality. You have to consider the lens you’re working with.
Photography is all about painting with light. Lenses are the tools you use to bend the light and the image can only contain the amount of detail and light that the lens lets through.
Most photographers agree the quality of the lens is generally more important than the quality of the camera. Put a crappy lens on the best camera in the world and you’ll get a crappy image. However, the reverse is not always true. You can still take nice images with a mediocre camera and a high-quality lens.
Faster lenses (i.e. better lenses) allow more light into the camera, which can help compensate for smaller photosites. In other words, if your camera is having trouble in low-light situations, using a better lens can help improve your image quality.
Generally speaking, a better lens will always produce better images regardless of the megapixel count. However, the reverse is not true. Using a mediocre lens on a higher MP camera will still produce mediocre results.
Does a Camera Lens Increase Megapixels?
If a better lens can improve the quality of an image, does that mean you can use a lens to increase the megapixels? No, the lens affects other qualities such as the amount of light entering the camera to produce a better image, but it does not affect MP.
Remember, megapixels are a physical count of the number of photosites present on the camera’s sensor. You can’t add or subtract those photosites by using a different type of lens. What matters is the number of megapixels and the size of your sensor. Those factors don’t change.
What Are the Disadvantages of Increasing Image Quality?
We’ve already mentioned that lower MP cameras tend to handle low-light situations better because the photosites are larger. Are there any other disadvantages of using a higher MP camera?
A big one for casual photographers is the size of the files. The files produced by higher MP cameras are large. You’ll need high-capacity memory cards and data storage solutions if you’re going to shoot with one of these.
Unfortunately, this can be prohibitively expensive for amateur photographers. Even professional photographers who don’t have a need for super high-resolution images often find this to be an unnecessary expense.
Another disadvantage is image processing speed. Unless you’ve got a powerful computer at your disposal, you won’t get the same snappy results when editing as you’ll get on lower resolution files.
How many megapixels do I need for landscape photography?
You may have heard that for landscape photography you should have the highest number of megapixels you can get. This is a myth.
Your final output should dictate how much resolution you need. For screen viewing, a 60 megapixel image is overkill, unless you plan on cropping it to a small part of the photo. Even a 42 MP photo has a resolution of 7952×5304 pixels, which is more than double the size of a 4K monitor. And thats IF you use a 4K monitor.
When it comes to print output, a 30 MP photo would give you a size of over 22 inches at 300 dpi, and a 24 MP photo a size of 20 inches at 300 dpi. For landscape photography, a 24 MP camera is plenty unless your goal is larger posters.
Choosing the Camera For You
Higher numbers of megapixels doesn’t always mean it’s a better camera for you. More megapixels doesn’t always mean better image quality, though it can be advantageous to have more MP in certain situations.
When you’re choosing a camera, you need to think about the type of photography you plan to do, the lenses you’ll use, and what sensor size will work best for your needs — as well as the number of megapixels.
To learn more about sensor sizes and understand the difference, check out this great explanation by photographer Benjamin Jaworskyj:
Still feeling a bit overwhelmed about what type of camera to choose? Check out our recommended gear page for some tips. The photographers here at Photodoto have compiled information about our favorite photography gear (and the gear we wish we had) to help you choose the best camera for your photography needs.