Removing Moir and Chromatic Aberration Effects

Noise reduction and artifact removal are often lumped together as similar phenomena. The truth of the matter is:

► Image noise is caused during image capture by the image sensor, and is more pronounced in shadow areas.

► Image artifacts are caused by color limitations in the image sensor's Bayer pattern and the subsequent in-camera color interpolation. Other artifacts can also be produced by oversharpening.

It is often difficult (or even impossible) to remove moiré effects using a RAW converter, so we often resort to using Photoshop instead (section 7.7, page 267). It is best to remove other lens-based artifacts, such as chromatic aberrations and vignetting, at the RAW conversion stage. ACR, Adobe Lightroom, Capture One, and Nikon Capture NX are all strong in this area. Lightroom and ACR even have separate Luminance Noise, Color Noise, Chromatic Aberration, and Defringe tools (figure 5-18). The latter is used to remove blooming effects caused by sensor elements overloading at high-contrast edges.

You can also reduce moiré effects in ACR and Lightroom by using the Adjustment Brush with a negative Clarity value. Capture One has its own dedicated moiré reduction tool.

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