Why do dark halos appear around silhouetted birds after editing a high-contrast RAW file?
Asked 12/25/2021
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I photographed brown pelicans flying against a bright sky with a Nikon P950 and processed the RAW file in Lightroom. After lowering exposure and making strong tone adjustments, I noticed dark halos around the birds. The halos remain with different highlight, shadow, white, and black slider settings, though they become more or less noticeable depending on the amount of adjustment. What causes these halos around high-contrast edges, and is this a sign of over-processing or something else?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
4y ago
2 Answers
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Operations that increase contrast often produces halos at high contrast edges.
Sharpening will also produce halos at high contrast edges.
When the halos detract from your intent, it can be a sign of over-processing the image. Though it is worth keeping in mind that intent can vary. Low resolution images tend to tolerate higher degrees of sharpening and contrast than high resolution images.
(Also, there appears to be some chromatic aberration on the edges as well when I zoom in. This is a result of both the character of the lens and not applying a mitigating filter in processing).
Originally by user95237. Source · Licensed CC BY-SA 4.0
user95237
4y ago
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Generated from our catalog & community — verify before relying on it.
Dark halos around the birds are most likely edge artifacts from processing a very high-contrast scene. Strong contrast adjustments can create halos along bright/dark boundaries, and sharpening can make them even more obvious. In a silhouette against a bright sky, those edges are especially prone to it.
So yes—this is commonly a sign that the image has been pushed too far in processing, particularly with contrast-boosting or detail-enhancing adjustments. Lower-resolution output can hide some of it, while viewing larger on a monitor can make it more visible.
There may also be some chromatic aberration at the bird edges, which can add colored fringing and make the problem look worse. That comes from the lens characteristics unless corrected in processing.
To reduce the effect, back off aggressive contrast/shadow/highlight or sharpening adjustments, and enable lens/chromatic aberration correction if available.
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