Eureka (eurekagray) wrote,

Fringe Removal

One fairly common problem with digital cameras is known as colour fringing. As a byproduct of the array of sensor sites on a modern imaging sensor, cameras sometimes have a hard time discerning edge and pixel-width details. The first image below is a crop (click to see it at 100%, i.e. that area is a segment 900 pixels by 600 pixels from the overall image) of a shot I've posted before. Until I got in close to look at it for an enlargement, I didn't notice the hard red edges to the lighthouse and some of the rebar. I very nearly passed on this image because of how strong the red edging was. With a bit of creativity, I managed to tone it down to something reasonable.

An image with colour fringing

Colour fringing removed.

To do this, I started with a Hue/Saturation adjustment layer. I desaturated the red channel across the tones represented by the fringing, but that caused the entire image to go dull (as I knew it would) so I masked out the change and carefully painted it back in along the thin lines. Even with the colour gone, the edges were problematic as they were too dark. After some experimentation, I went back into the Hue/Saturation layer and increased the Lightness so the edges blended more naturally with the tone of the rest of the lighthouse. The end result is a pretty good fix. I left a hint of the red colour in, as there is so much in the surrounding area it's not distracting, and likewise left a bit of the darker tone to add to edge sharpness. I'm pretty confident it will hold up well as a large print.
Tags: air, architecture, beach, colour, digital, earth, fire, manipulation, sunrise, tutorial, water
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