What You Should Know about Pixels and the File Size of Your Digital Photos

By Julie Adair King

Many factors affect the size of the data file needed to store a digital picture, including the complexity of the scene (the level of detail, the number of colors, and so on). The file format in which the image is stored, usually either JPEG or Raw, also affects file size. But all other things being equal, an image with lots of pixels has a larger file size than a low-resolution image.

Although more pixels translates to better prints, the large files needed to contain those pixels create several problems:

  • Large files require more storage space. When you’re shooting huge files, it doesn’t take too long to fill up a camera memory card, computer hard drive, or a cloud (online) storage account. And if you archive your files on DVD, which is recommended for your most treasured images, you can wind up with a huge disc collection in no time, given that the maximum storage capacity of a DVD is about 4.7GB, or gigabytes. (One GB equals 1,000MB.)
  • Large files take longer for the camera to capture. The more pixels you ask your camera to capture, the longer it needs to process and record the picture file to your memory card. That additional capture time can be a hindrance if you’re trying to capture action shots at a fast pace.
  • Large files strain your computer. Large files make bigger demands on your computer’s memory (RAM) when you edit them. You also need lots of empty hard drive space for editing because the computer uses that space as temporary storage while it’s processing your images. (This temporary storage is sometimes referred to as virtual memory or scratch disk space.)
  • Large files are inappropriate for online use. When placed on a web page or sent via email, photos that contain bazillions of pixels are a major annoyance. First, the larger the file, the longer it takes to download. And if you send people a high-resolution image in an email, they may not be able to view the whole image without scrolling. Remember, most computer monitors can display only a limited number of pixels.

All that said, large files are a fact of life if you want to capture images at your camera’s highest resolution and quality settings. But do consider whether you always need to max out the pixel count. Are you really going to want to print the picture of your grandma’s birthday cake or your new car at 8 x 10 inches or larger? If not, dialing down resolution a notch makes sense.