Understanding aliasing and anti-aliasing techniques in photography.


A person walking and staring down at their mobile phone

Patterns causing your image to glitch? That’s a moiré problem.

Sometimes called moiré or a glitch, aliasing is a phenomenon where a digital camera has trouble translating an intricate pattern. Aliasing can result in a number of odd visual artifacts in photos or videos. For example, a person’s finely striped or patterned shirt can cause strange waves or swirl patterns to appear over it in a digital image. The waves or swirls, called a moiré pattern or moiré effect, are just one type of possible outcome. Aliasing can also cause color noise, tone jumping (random color changes), or jagged edges or pixelation across lines and boundaries (sometimes called jaggies).


“Aliasing is basically an artifact that makes an image look particularly digital in a disagreeable way,” says photographer Philip Heying. “It’s caused when digital information is broken down into pixels and bits; little tiny particles that are laid out in a grid. Sometimes, when information that you’re seeing in the real world meets that grid of the digital world, it’ll cause this objectionable moiré pattern or strange color shift that doesn’t look like what you’re seeing.”

A sphere wireframe
A cube wireframe

Different types of anti-aliasing.

Anti-aliasing refers to the programs and techniques you can use to avoid aliasing, or visible moiré, in digital projects. It only takes a short journey through Google to see that it’s not just a concern in the photography world. High-quality anti-aliasing is necessary in the computer graphics and ​video game industries, as well, and deals with the processing power of graphics cards. Essentially, a type of anti-aliasing may be needed by anyone from photographers to gamers dealing with digital signal or image processing or the translation of complex scenes into lower-resolution images. See how to smooth out aliasing in graphic design


Where to look for aliasing in photos.



“I did architectural photography for a while, and I would encounter it every now and again on a roof or the side of the building,” says photography professor Adam Long. 

Aliasing of a texture in a digital photo

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.



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.



Move closer or change angles.



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. 

Anti-aliasing in Adobe Photoshop

“Sometimes I’ll make my image on the monitor as small as a postage stamp, and then I’ll zoom in 400 percent to make sure all of it is cohesive and coherent,” says Heying. “By the time I go to make a print, there are no surprises. Maybe do a test print and see if it’s showing up and how it looks in your print.”


It’s always best if you can catch any aliasing issues before you get to post. Aliasing can affect the edges of selections with the Magic Wand tool, Quick Selection tool, or any selection method. But, as with any corrective edit, there are several ways to go about anti-aliasing in editing. Finding the right method is all about trial and error. 


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