To see a quick example of aliasing in a photo, hold your phone’s camera up to your computer screen and snap a picture of an area of your screen that’s mostly blank. Try a few different angles, and you’ll notice wavy lines or a moiré appear in your image. This aliasing is the result of your phone’s camera trying to make sense of the microscopic grid that makes up your computer screen.
Ways to fix aliasing during a shoot.
Avoid aliasing in real time while shooting photos by using filters built right into your camera or different shooting techniques. Explore these anti-aliasing methods to learn how.
An anti-aliasing filter in your camera.
Some cameras include a physical anti-aliasing filter, also known as an OLPF, or optical low pass filter. This analog filter adds a very low level of blurriness to your photos that prevents just enough level of detail in small patterns to eliminate aliasing. However, the higher resolution a camera is, the more likely it is to be able to resolve the details of fine patterns without an anti-alias filter. As camera technology advances, many high-definition cameras don’t include an OLPF, or they give you the option to purchase the camera without it.
Stop down your lens.
No matter how good your camera is, there is always the chance for aliasing if you are far enough away from a pattern or hit it from the wrong angle. Try stopping down your lens to its smallest aperture. Small apertures encounter diffraction, which will slightly soften the image and can get rid of aliasing.
Move closer or change angles.
Another way to remove aliasing if you see it in your original image is to get closer to your subject or change your angle. When you get closer or magnify something that may become a moiré or interference pattern, it’s easier for your camera to read it.
Ways to fix aliasing in post-production.
If you don’t notice a moiré pattern or aliasing while shooting, or you can’t prevent it, you can correct it in post-processing in several ways, with digital filters and effects in Adobe Photoshop or Lightroom.
Double-check for aliasing at different sizes.
Check your images each time you resize. When you create downsamples, or copies of your image in lower resolutions, areas that you didn’t think needed to be anti-aliased may start to pose a problem.