Halos - What causes them?

The photo below is a heavy crop (close to 100%). I processed it in LR5.3 (I can do a screenshot of the develop module later).

Obviously some aspect of my developing caused the halo around the bird. My question is - what aspect caused it? I know I hit the 'Auto' button as my starting point, adjusted more to my liking, used some clarity, bumped saturation, and added some sharpening.

Halos are my least favorite things, and I'd like to avoid them in the future.

That's called sharpening.

Sharpening creates halos around areas of contrast to emphasize their presence, because to our eyes, contrast = detail. Light areas get lighter, dark areas get darker, and the size of the halo depends on the "radius" setting of the sharpen.

Typically, this artifact isn't very visible where lots of detail is present, but can be annoying when it comes to boundaries between continuous tones, such as between the sky and landscape, or like in your case. Normally, what I do for such images is put the sharpening on a new layer in Photoshop and mask out the offending edges, or just exclude the color blue from being sharpened if it's above a certain RGB value.

That's what I was thinking, that it was the sharpening. I'm not really good at changing settings, so does using different radii and the others help?

Did you move the colour sliders? That introduces halos too.

KirkS518 wrote in post #16542738
That's what I was thinking, that it was the sharpening. I'm not really good at changing settings, so does using different radii and the others help?

Your problem is as you said, the image was close to a 100% crop, and because of that the amount of sharpening that would be normal for a minimally cropped shot is way too much for this one. Sharpening is absolute, not relative; a radius of 1 means that the halo will be 1 pixel wide, and a radius of 2 means 2 pixels wide.

For a 100% crop I would suggest a radius of 0.7 to 0.9 and an amount of 120 to 160.

The "masking" parameter in Lightroom, or "threshold" in Photoshop's sharpen tools, determine how much contrast there must be between two pixels before they get affected by the sharpen. A threshold/masking of 0 means all pixels get sharpened, while a larger value means only very contrasty edges get sharpened, while areas of low detail are ignored.

Edit: Another parameter that can introduce halos is the "clarity" slider, when set to any positive amount, but these halos usually have a very wide radius.

Kolor-Pikker wrote in post #16542755
Your problem is as you said, the image was close to a 100% crop, and because of that the amount of sharpening that would be normal for a minimally cropped shot is way too much for this one. Sharpening is absolute, not relative; a radius of 1 means that the halo will be 1 pixel wide, and a radius of 2 means 2 pixels wide.

For a 100% crop I would suggest a radius of 0.7 to 0.9 and an amount of 120 to 160.

The "masking" parameter in Lightroom, or "threshold" in Photoshop's sharpen tools, determine how much contrast there must be between two pixels before they get affected by the sharpen. A threshold/masking of 0 means all pixels get sharpened, while a larger value means only very contrasty edges get sharpened, while areas of low detail are ignored.

Edit: Another parameter that can introduce halos is the "clarity" slider, when set to any positive amount, but these halos usually have a very wide radius.

Thanks! The bold is very helpful - it's something I didn't know.

http://www.youtube.com …M0WI0fC_PujkGoL​MyXWXd3yF7

This video does a good job of showing your how sharpening, and other tools in LR affect edges and how you might get halos.

Hold down the Alt key as you move the Masking slider and you will be able to see what is being masked. As areas are masked they turn black.

Hold down the Alt key whilst using the Amount, Radius, Detail and Luminance sliders. This give you a B/W preview that is often easier to spot halos and judge the changes you are making.