What causes the HDR "halo" and how do you get rid of it?

Discussion in 'Photography Beginners' Forum' started by inTempus, Apr 10, 2009.

  1. inTempus

    inTempus TPF Noob!

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    I've noticed that most of the HDR images I've done (not very many at all) and others that I've seen posted have this halo of light around the subject.

    Example:

    [​IMG]

    It's obvious around the buildings.

    What can be done in Photomatix to get rid of this halo? Or is this something inherent to HDR's and has to be dealt with using special Photoshop-fu?
     
  2. rufus5150

    rufus5150 TPF Noob!

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    It's not any one thing, it's the combination of controls which boost contrast. Light smoothing is often the granddaddy of halo creation and microcontrast can induce some as well.
     
  3. Mike_E

    Mike_E No longer a newbie, moving up!

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    Information that doesn't exist would be my guess. Stretch the curves that much and you are bound to thin out the original and find the white underneath.
     
  4. tsaraleksi

    tsaraleksi TPF Noob!

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    It only makes sense that when you are relying on software to decide what should be light and what should be dark, and dealing with radically different exposures, that it will be screwy. The best way I can think of to fix it would be to just do the exposure layering by hand.
     
  5. Marc Kurth

    Marc Kurth TPF Noob!

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  6. Marc Kurth

    Marc Kurth TPF Noob!

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    Was that from a single raw image, or actual multiple exposures? If so, how many?

    I noticed that HDRsoft was looking to hire some new programming talent awhile back. One of the items that would put your resume near the top of the pile was the ability to express ideas on how to perform halo reduction in their software.

    Marc
     
  7. inTempus

    inTempus TPF Noob!

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    It was composed from (7) individual shots, bracketed by my camera.

    I hope they figure out a way to reduce that halo. :) It would make me buy their software all over again.
     
  8. Arch

    Arch Damn You! Staff Member Supporting Member

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    Its not really much to do with amount of exposures or info.

    My best explanation of what happens, from what i know already, is that it is more to do with local contrast... the tone mapping stage.

    Areas which need alot of dynamic range information, like buildings, tree's etc will be making full use of the under and over exposed images which make up the HDR. What the software struggles to do, is restrain that information to a very tight area of the image.
    This is why you can increase and decrease the amount of halo buy changing strength, light smoothing and micro contrast.
    You are effectively allowing the software to either give you a large contrast definition area, making the HDR look stronger but also making halo's large. Or you can make the contrast more controlled, having a lesser HDR strength but also producing less halo's.

    Basically, the software is not yet able to control the area of spill out, and it is especially obvious when the area which has the most range is next to an open space or sky.

    Im not sure what the makers of Photomatix would say, but my take is just by observation and knowledge of HDR.
     
  9. George Hawkins

    George Hawkins TPF Noob!

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  10. inTempus

    inTempus TPF Noob!

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  11. inTempus

    inTempus TPF Noob!

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    I was over at the inlaws today for Easter dinner. Of course I use every possible opportunity to go shoot something. I snuck out of the house and ventured around the woods a little to get some pictures. I wanted to try a different HDR and see if I could work on the halo based upon some feedback here.

    I think I got rid of most of it in this image... but then I've been staring at it for an hour... I probably just can't see it anymore. :) I know the subject isn't particularly exciting, but I was more looking for something that would make a decent HDR than I was trying to find that perfect subject.

    [​IMG]
     

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