In digital photography, an artifact is any unintended visual element in an image that was not present in the original scene. Artifacts are introduced by the camera sensor, image processing, or file compression. While some artifacts are barely noticeable, others can significantly degrade image quality.
Common Types of Artifacts
Compression artifacts appear when images are saved in lossy formats like JPEG. At low quality settings, you will see blocky patterns, color smearing around sharp edges, and loss of fine detail. These are most visible around high-contrast boundaries, such as text against a solid background or branches against a bright sky.
Moire patterns occur when fine, repeating patterns in a scene (like fabric weave or building facades) interfere with the pixel grid on the sensor. The result is wavy, rainbow-colored patterns that were not in the original scene. Cameras without an anti-aliasing filter are more susceptible to moire.
Banding shows up as visible steps in what should be smooth gradients, such as a blue sky transitioning from light to dark. This typically results from insufficient color depth or aggressive editing of 8-bit files.
Chromatic aberration produces color fringing, typically purple or green outlines along high-contrast edges. While technically a lens aberration rather than a digital artifact, it appears frequently in photographs and is correctable in post-processing.
How to Minimize Artifacts
- Shoot in RAW format to avoid compression artifacts at capture
- Use the highest JPEG quality setting when RAW is not an option
- Avoid excessive sharpening, which amplifies noise and creates halos
- Be cautious with aggressive shadow recovery, which can introduce banding and noise
- Export final images at appropriate quality levels for their intended use
Most RAW processors include tools specifically designed to address common artifacts. Lens correction profiles fix chromatic aberration automatically, while noise reduction algorithms target sensor-generated artifacts. Understanding what causes each type helps you both prevent and correct them effectively.
Common Types of Image Artifacts
JPEG compression artifacts are the most frequently encountered type. When you save an image as JPEG, the algorithm divides the image into 8×8 pixel blocks and discards fine detail information to reduce file size. At high compression (low quality settings), these blocks become visible as a grid pattern, especially in smooth gradient areas like blue skies. Each time you re-save a JPEG, the compression is applied again, progressively degrading quality — this is why photographers shoot in RAW format and only export to JPEG as a final step.
Banding appears as visible steps in what should be smooth tonal transitions. This typically occurs when working with 8-bit images that only support 256 tonal levels per channel. A sky gradient that transitions smoothly in 14-bit RAW can show obvious bands when compressed to 8-bit JPEG, especially after heavy editing. Working in 16-bit mode in Photoshop and adding a tiny amount of noise (0.5-1%) to final exports helps mask banding in gradient-heavy images.
Optical and Sensor Artifacts
Moire patterns occur when fine, repetitive details in a scene — like fabric weaves, building facades, or fence wires — conflict with the regular grid pattern of your camera sensor’s pixels. The interference creates rainbow-colored wavy patterns that do not exist in the real scene. Cameras without optical low-pass filters (like many high-resolution bodies) are more susceptible. Slightly changing your distance or angle to the subject often resolves moire in the field.
Chromatic aberration manifests as colored fringing along high-contrast edges, particularly toward the frame corners. Purple and green fringing (lateral CA) results from different wavelengths of light focusing at slightly different points. Lightroom’s Lens Corrections panel handles this automatically for profiled lenses, and the manual Defringe sliders can remove stubborn fringing that profile corrections miss. Longitudinal CA appears as magenta fringing in front of the focal plane and green behind it — it is most visible at wide apertures and diminishes as you stop down.