The moiré effect is something you may have noticed in a photo before and not realized it had a name. Usually undesired and unintentional, moiré (or the moiré effect or moiré pattern) refers to unusual and repetitive lines, dots, or colors that show up in images with fine detail. Below we elaborate on what causes moiré in photography, and the different ways you can detect, avoid, and remove it.
What is Moiré in Photography?
Generally speaking, moiré refers to the visual of a pattern overlaid on top of another pattern that is similar, but not exactly the same. Moiré patterns are a type of interference pattern, and like the golden ratio, originates in mathematics and physics.
In photography, moiré only became an issue once digital photography was invented. An image sensor is what allows a digital camera to create an image without using film, and is effectively a grid of megapixels. When photographing an object that also has a pattern, the resulting moiré effect caused by the two patterns can distort the final image. The unique distortion caused by a moiré pattern is known as aliasing.
Aliasing can occur when shooting a variety of objects, such as fabrics, architecture, bird feathers, hair, or any fine patterns. One of the easiest ways to see the moiré effect is to try and take a photo of a computer or TV screen.
The effect can be subtle, and you won’t be able to see it through a non-electronic viewfinder. You may not even notice until you review your images on a larger display, long after you’ve stopped shooting.
How to Avoid & Remove Moiré
One of the best things you can do to combat the moiré effect is to upgrade your camera. Modern digital cameras tend to have a built-in filter over the sensor that is designed to reduce aliasing. This is known as an anti-aliasing or optical low-pass filter. Some cameras allow you to disable this feature, as it can soften your imagery.
Upgrading to a higher resolution camera also helps prevent the moiré effect. A higher resolution means the sensor has more megapixels, allowing it to capture more detail in your imagery and reducing the likelihood of aliasing. Some advanced camera models don’t even have an anti-aliasing filter, as the moiré effect is already mitigated by a high resolution.
If you’re not ready to upgrade your camera, there are a few other steps you can take to minimize the risk of moiré.
Take test photos
If you have the flexibility to get your photo just right, take some test shots and look for any distortions (for color moiré, look for yellows, purples or greens). If your camera has an LCD display, zoom in on the image after taking it to check for aliasing. Find ways to change any problem areas, and retake the photo.
Shoot from a different position
Since moiré effects arise from an overload of detailed patterns, getting closer to the subject and making those patterns easier to capture can solve your issues. Depending on the situation, this can mean optically zooming in or physically moving closer. Shooting from a different angle can also help.
Adjust your aperture
Experimenting with different apertures can help eliminate moiré. Using a smaller aperture (that is, a higher F-stop) can often help. When shooting at a small aperture (such as F16 or higher), diffraction softens the image, ultimately helping to reduce aliasing.
Fix it in post
Do not be discouraged if you notice aliasing in your photos. Moiré in photography is quite common, but its effect can be minimized or removed using the techniques above. Understanding why it happens, and what can be done to prevent it, is an essential step towards mastering photography.