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Thread: Avoiding HDR artifacts?

  1. #1
    neverhood311's Avatar
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    Avoiding HDR artifacts?

    I'm using Qtpfsgui 1.9.3 to create HDR images and tonemap them. However, when I generate the image at the full resolution of 10.1 megapixels, there are tiny artifacts in many places where the brightest and darkest exposure 'meet up.' Here's an example screenshot:

    Avoiding HDR artifacts?

    What can be done to avoid this? The shots were taken on a Rebel XTi atop a tripod (a cheap-o $15 one) and unfortunately I forgot to grab my cable shutter release so I'm touching the camera when the shutter goes off. The slowest exposure is 1/2 second and the fastest is 1/30th second. Would a better tripod help? Would a cable shutter release help? Does anyone else have these problems?

    So far, what I've been doing to remedy the problem is painstakingly going through the image and painting in each of the 'off' pixels one by one. It's taking hours, though. I don't think I wanna do that again.

  2. #2

    Re: Avoiding artifacts?

    use TUFUSE or Zeronoise, the result is more real

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    Klickit's Avatar
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    Re: Avoiding artifacts?

    I have had haloing too, but not as extreme as this. I use Essential HDR. If I really care about an image, I do go around the haloed areas, but it's a bit of a time-pain. I think there may be a way of reducing the haloing using layers and blend modes, but alothough I've experimented, no luck. Maybe one of our PS gurus might have some ideas?

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    timo2's Avatar
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    Re: Avoiding artifacts?

    Quote Originally Posted by neverhood311 View Post
    I'm using Qtpfsgui 1.9.3 to create HDR images and tonemap them. However, when I generate the image at the full resolution of 10.1 megapixels, there are tiny artifacts in many places where the brightest and darkest exposure 'meet up.' Here's an example screenshot:

    Avoiding HDR artifacts?

    What can be done to avoid this? The shots were taken on a Rebel XTi atop a tripod (a cheap-o $15 one) and unfortunately I forgot to grab my cable shutter release so I'm touching the camera when the shutter goes off. The slowest exposure is 1/2 second and the fastest is 1/30th second. Would a better tripod help? Would a cable shutter release help? Does anyone else have these problems?

    So far, what I've been doing to remedy the problem is painstakingly going through the image and painting in each of the 'off' pixels one by one. It's taking hours, though. I don't think I wanna do that again.
    I don’t know Qtpfsgui but in Photomatix you can auto align the source images; even handheld images line up perfectly.

    “tiny artefacts” is not how I’d describe them, I’d call them gross distortions!

    BTW you can get very low cost wireless remotes (see eBay) as an alternative to a cable release.

  5. #5
    neverhood311's Avatar
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    Re: Avoiding artifacts?

    Quote Originally Posted by timo2 View Post
    I don’t know Qtpfsgui but in Photomatix you can auto align the source images; even handheld images line up perfectly.
    I'd love to use Photomatix but I'm on a really tight budget right now.

    Yesterday I was out taking some photos at a river and I set up for HDR. I think I did everything right: I firmly secured the tripod, I used the cable shutter release, and I still got the same "gross distortions" as before as well as some serious banding in the blue sky. I noticed that these aren't coming from the tone mapping, but the HDR compilation. At any rate, I've got some investigating to do.....

  6. #6
    timo2's Avatar
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    Re: Avoiding artifacts?

    What happens if you run the same files through the demo version of Photomatix? Banding is usual only evident when working on 8bit files and is worsened by heavy processing.

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    David's Avatar
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    Re: Avoiding artifacts?

    Hi Justin - Which tone-mapping option were you using with Qtpfsgui? Some of the options are very sensitive to minor changes in parameters.

    Also, Qtpfsgui allows single image processing. Have you tried that on, say, the mid-range image to see if the artefacts appear?

    David

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    Re: Avoiding artifacts?

    "I'd love to use Photomatix but I'm on a really tight budget right now" - there are some free apps - Zero Noise (there's a thread about it here, somewhere...) and Picturenaut, which has an "Align" option, which can help.

    How are you changing the exposure value between shots? I've found that using a really light touch necessary.

    HTH

    Peter

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    neverhood311's Avatar
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    Re: Avoiding artifacts?

    Quote Originally Posted by David View Post
    Hi Justin - Which tone-mapping option were you using with Qtpfsgui? Some of the options are very sensitive to minor changes in parameters.
    I always use the 'Manituk' option for tone-mapping. I think it offers a fairly realistic effect while making the image pop.

    Update: I did some more fiddling around and I found out that if I shoot in RAW and compile the HDR in Photoshop instead of Qtpfsgui, then tone map in Qtpfsgui, the artefacts almost disappear. I'm gonna try a few more just to be sure.

  10. #10
    David's Avatar
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    Re: Avoiding artifacts?

    Hi Justin - I've used the Mantiuk tone-mapping algorithm many times and I have not come across this particular problem with it. I posted some technical notes on Mantiuk a while back. Qtpfsgui Notes - Manntiuk TMO There may be some info in there that is relevant. Also download the free trial version of HDR Photostudio, and/or Picturenaut (free): http://www.unifiedcolor.com/ http://www.hdrlabs.com/picturenaut/

    Both these allow you to create an HDR file that you can store and tone-map in other software.

    Cheers

    David

  11. #11

    Re: Avoiding HDR artifacts?

    You use the software, which allows exposure fusion.

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