what is the cause of halo around dark objects (non-HDR)

Question

This problem occurs often with scenes that have trees with the sky behind. I tend to raise the shadows and reduce the higligts (in RAW) to get a more pleasing image, I believe this is a normal thing to do.

Here is a [extreme] demo, original shot:

after raising the shadows (I raised more than usual to make the problem show more):

As you can see, dark has bright halo and bright has dark halo and I noticed that the darker the image the more apparent the effect. Here are my questions:

Is this a hardware or a software post processing artefact?
if it's hardware then do I have a faulty camera or is this normal?
is this the same problem that occurs with HDR shots?

and of course, can it be fixed?

The image was taken with a Sony a6300, 10-18mm lens

EDIT:

software used: tried both Luminar 2018 and Darktable
the attached images are just screenshots directly form the editing software

For completeness: what software do you use to process the RAW file? The actual adjustments done in the image might differ per software package. — Saaru Lindestøkke, Jan 16 '20 at 14:05
It's possible to ameliorate it a bit - see https://i.stack.imgur.com/RCViq.jpg - but I'm wondering if the Sony has some kind of internal contrast modifier like Nikon's Active D-Lighting… see this Q & A - https://photo.stackexchange.com/questions/93500/what-causes-this-dark-halo-around-the-sun — Tetsujin, Jan 16 '20 at 14:18
@Tetsujin how did you ameliorate it? is it a feature or you did it manually? — Fanckush, Jan 16 '20 at 14:29
@SaaruLindestøkke see update question, I used Luminar and darktable. I don't have access to LR to test this but I could upload the .ARW for someone to test if needed — Fanckush, Jan 16 '20 at 14:32
That was just using the front page of Adobe PhotoRAW [white/black/high/low & a little clarity] with a bit of de-noising, as the image was so small. 2 mins work. You could do a lot better on the full-size original. — Tetsujin, Jan 16 '20 at 14:47
To clarify: You're using a "shadows" slider to brighten the image? If so, the halo is likely related to how the algorithm isolates the shadows. — xiota, Jan 16 '20 at 18:06
It's all HDR (High Dynamic Range Imaging) when you are squeezing a wide DR scene into a display medium with less DR than the scene contains. — Michael C, Jan 17 '20 at 00:31

score 1 · Accepted Answer · answered Jan 16 '20 at 18:50

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It is a processing/software artifact and the same as what is encountered when tone mapping HDR images... that's basically what you are doing; re-mapping the tones, only w/in a single image.

Also check other contrast type settings; sharpening, clarity, etc. Those types of settings try to preserve/increase the perception of details by adding localized contrast; i.e. light next to dark/dark next to light.

answered Jan 16 '20 at 18:50

Steven Kersting

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so this is the result of local contrast? seems like the software I'm using is adding clarity internally when I increase the shadows and reduce the highlights – Fanckush Jan 16 '20 at 20:02

score 0 · Answer 2 · answered Jan 16 '20 at 20:30

Confirming @Steven Kersting's answer, the problem is a software issue caused by some internal tone mapping/local contrast, the "shadows" slider shouldn't normally cause the hallo but in this case it is.

I managed to fix the halo problem using RawTherapee, by sliding the shadows slider I got the results I was expecting (without the halo). This indicates different implementation of the feature, which in my opinion is more accurate:

what is the cause of halo around dark objects (non-HDR)

2 Answers2