First, a Brief History of Resolution
Just a few years ago, 10 megapixels of image resolution was enough to be considered high. Now, though, even the most basic digital cameras typically offer 20 megapixels of resolution. High-end DSLRs can offer as much as 60 megapixels or more, such as the Sony Alpha a7R IV. In fact, 2019 saw Samsung unveil a smartphone camera that offers 100 megapixels. There’s no strict standard for what constitutes high resolution, and what’s considered high-res today will change as technology improves. In that way, high resolution is a relative designation, and it’s less important on the list of specs when you’re shopping for a new camera—because most new cameras offer ample resolution.
So, What’s a Megapixel, Anyway?
A pixel is an extremely tiny individual area on the image sensor that measures the amount of light that travels through the camera lens and strikes it. A digital photograph combines all of the pixels that the image sensor can measure. One megapixel is equal to 1 million pixels. So, an image sensor that contains 20 megapixels has 20 million individual areas where it can measure light.
Resolution and Print Sizes
The typical inkjet printer delivers its best quality at 300 dots per inch (dpi). So, to calculate the resolution you need for a print, start with the size print you want, and divide the dimensions by 300. Let’s say you’d like a 10- by 13-inch print. To calculate the megapixels you need, the formula looks like this: (10 inches X 300) X (13 inches X 300) / 1 million = 11.7 megapixels Going in the other direction, let’s say you have a 10 MP photo. It contains 2592 by 3872 pixels, which would give you a good-quality 8.5-by-13-inch print. Photos to be used online don’t require nearly as high of a resolution. Generally, assuming you have enough room on your media, it’s a good practice to shoot everything at the highest resolution available; you can trim this back later for various purposes, but you can’t go back and add pixels.
Other Things to Consider
All the math aside, though, the quality of your photos depends on far more than resolution. All digital cameras of a particular resolution won’t yield the same image quality. Lens quality, image sensor quality, and response times of the camera all play a role.
Shooting a Great Photo
Rather than worrying about the maximum resolution at which you can take a photo, make sure you’re shooting with proper exposure and in good lighting to ensure the best possible image quality. You’ll be much happier with your photography if your subject is interesting, your shot is well-composed, and accurate focus gives you the sharpness and/or effect you want. Also note that a camera with a larger image sensor is going to create a higher-quality photo than a camera with a smaller image sensor, even if the cameras offer the same amount of resolution. So, resolution and megapixel counts aren’t the only aspects to consider when shooting. A good rule of thumb is to shoot for quality, not so much for quantity.
