Halo

[Tom Rambaut]

Having just had a halo pointed out in one of my photos I was just wondering how this is happening from a technical point of view. What is going on?

Thanks Tom

[WIlliam Maroldo]

A large halo can be the result of improper use of the Shadow/Highlight tool in PS. A bright very narrow halo results from improper use of Unsharp Mask and other sharpening methods.
regards~Bill

[Chris Ober]

Over aggressive use of HDR software setting can generate some pretty obvious halos too.