Terribly looking spots on HDR image

This is a discussion on Terribly looking spots on HDR image within the IR & HDR Photography forums, part of the PHOTO GALLERIES category; Hi, when I am usualy merging the HDR image, the result looks a bit strange. I have no idea, why the result image contains so ...


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  1. #1

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    Hi,

    when I am usualy merging the HDR image, the result looks a bit strange. I have no idea, why the result image contains so strange spots:

    could it be becouse of highlights?
    It happens after using Photomatix and even Photoshop.

    Now I tried image, that represents the second problem, which I have with HDRs. Have a look. This is photograaph which I merged in Photomatix. I had three sources {-2; 0; +2}. Canon 400D, ISO 200, {1/25, 1/100, 1/400} I used the ND8 filter to make it more "smooth". This is the result {100%}:



    Does`nt it looks terribly?! What the **** is wrong?

    Thanks


  • #2
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    PHOTO EDITING NOT OK
    The only thing I could suggest is not going so far apart with the EV's. try useing +1 & -1 It won't be as extreme, or even try useing all five +1, +2, -1, -2, & 0, and see what happens.
    It's all trial and error, and we've all done it, in fact, some of still do regularly....lol
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  • #3

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    Ok I`ll try more expositions.

  • #4
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    PHOTO EDITING NOT OK
    if it helps, maybe you can provide the three exposures so we can have a better look into your problem by working it ourselves?

  • #5
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    PHOTO EDITING OK
    Were these shot using RAW format, or JPG? (I've seen this effect also, but can't remember if I used RAW or JPG).

    Looking at your camera specs, you're able to shoot RAW files to .CR2 format. So if you're not shooting RAW, try it. It may be that there's just not enough info in the JPG file for it to work with.

    You're also able to set your ISO to 100 at the lowest. I don't know if that is helping (or, not helping) the image quality in these.. but the lower the ISO the better for HDR files (to avoid noise best you can).

    I don't think it's the settings you're using in photomatix (as far as the "blobs" go anyway. The quality of the photo in general may benefit from more tweaking in different settings though). When those "blobs" happened to me, I tried all different settings, but the artifacts were still there (they were there before I even started tonemapping, right after I merged the images.. same with you?) so I think it's how the images are being brought to photomatix to begin with (file format/ISO/exposure ranges, etc.), not the settings your using.

    It might also be highly exposed areas clashing with under exposed areas when files are merged. If that's the case, lesifer's tip may be helpful.

    But I could be wrong. I never found an answer to it, I just re-shot the scene instead. And I don't remember the key aspects of how I shot it, I just remember it happening. So this is all just off the top of my head.

    Now you've got me intrigued to find the answer. I may try to shoot some stuff to get the effect again so I can troubleshoot it myself! (but of course, when I want it to happen, it won't now. I'll probably get perfect HDR images! arg! hah)
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  • #6
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    okay, scratch the JPG/RAW comment.
    I tried to recreate it, but failed.

    So I thought about what photos I've taken that had the effect (the greyish "blobs" like in your photo) and remembered one, and found it on my computer and ran it through photomatix. Yep, still got the blobs. And they were RAW files. So yeah. Scratch the JPG comment (but still, if you are shooting JPG, try RAW just to get that much more data on the image for photomatix to work with).

    But looking again, I didn't notice the DNG image before in your post. So I guess you *are* shooting RAW. DNG isn't the RAW file format for that camera though. So I'm guessing you're converting the CR2 file to DNG before you throw it into photomatix? I've never used DNG files or converters.. so I'm not sure how that goes. Try just loading the CR2 files into photomatix. I doubt it'd help with these problems in this photo, but I just don't see a need to convert it to DNG first. Better to just let it run off the original RAW file then let another program mess with it first before it gets there, ya know?

    But anyway, I looked at my 3 RAW files I tested with, and noticed that the areas that had the "blobs" when put into photomatix were areas where, on the RAW files, highly overexposed areas met darker areas.

    So I'd go with lesifer idea. Try to step down your exposure brackets so you don't get that clash of highly exposed with darker as badly.
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  • #7
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    Also (this topic has me going crazy to trouble shoot it! heh) while researching this.. I came across this:
    http://photography-on-the.net/forum/...d.php?t=236308

    The guy there is mentioning alot of different things about his HDR image, but one of the things is the same "blobs" like on your image. The first image (his HDR), notice the car lights on the bridge. Same greyish blob effect. Although no one on that forum gave a reply to why that happened.. I think it's because, between his 8 shots, sometimes there were cars going by, and sometimes there weren't. So in the end HDR merge, the light of the car headlights in some photos merged with the darkness of there being no headlights in the same area in other photos. It clashed, and it didn't like that.

    That explains why the street lights at the bottom of the photo still look good. They were static, always there and lit. So they came out nicely compared to the car lights on the bridge which were there one second the gone in the next shot.

    Also, notice in the very right side bottom corner area. There's some blobbing also. Looking at the original image below it, these are traffic lights. As the lights changed from green to red throughout his shots, it caused it to be exposed brightly in one shot, then when the light changed, be dark in the next shot.. causing the exposure clash.

    As for the rest of your photo (since the whole photo isn't just "blobbed out"). I'd say just keep messing with different photomatix settings. If you still don't get decent results, sometimes photos just are not HDR worthy (scene wise, not photo taking skill wise) and won't look "HDR like" no matter what you do.
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  • #8

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    PHOTO EDITING NOT OK
    If I had to guess, I would say that the exposure is not correct. I have had problems with the same kind of "blobs" and it is usually because I severely over or underexpose a portion and then the software tries to bring back detail in those areas.

    When I expose my images I always check the histogram. On your lightest shot, make sure that there is not information touching the left side of the histogram. On your darkest shot, make sure there is nothing touching the right. Then make sure you have at least one good middle exposure.

    Best I can tell ya. Keep playing with it. You'll figure it out with some experience.
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