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Thread: Why Is It So ?

  1. #1
    dje's Avatar
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    Why Is It So ?

    This is an image I took on the BC Ferry returning from Vancouver Is to Vancouver. Conditions were fairly hazy and by no means ideal however I took the shot as it was there and I had nothing to lose. It was clearly badly under-exposed but the thing that puzzles me is why the black level was so high. (see the histogram in the first image). After levels correction, it came up OK (with maximum noise removal in ACR). Can any one explain please ?

    Dave

    Without levels correction.
    Why Is It So ?

    With levels correction
    Why Is It So ?

  2. #2
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    Re: Why Is It So ?

    Quote Originally Posted by dje View Post
    This is an image I took on the BC Ferry returning from Vancouver Is to Vancouver. Conditions were fairly hazy and by no means ideal however I took the shot as it was there and I had nothing to lose. It was clearly badly under-exposed but the thing that puzzles me is why the black level was so high. (see the histogram in the first image). After levels correction, it came up OK (with maximum noise removal in ACR). Can any one explain please ?
    I would say that the haze diffused the mountain highlights and at the same time contributed some luminance to the shoreline. The camera faithfully recorded the resultant low-contrast scene - unlike your brain, which no doubt compensated nicely for the signals sent from your optic nerves. And if you had exposed more to the right the "black level" might have been even higher.

    My two cents worth and about the same value . . .

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    Re: Why Is It So ?

    Actually I think it is the mid tones in the first picture that are high. If it were the blacks that were high it would be high on the left side. Must have been a beautiful ride.

  4. #4
    dje's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by xpatUSA View Post
    My two cents worth and about the same value . . .
    Not too sure about that Ted. Your reasoning may well be correct, I'll see what others have to say.

    Thanks
    Dave

  5. #5
    dje's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by Muriel View Post
    Actually I think it is the mid tones in the first picture that are high. If it were the blacks that were high it would be high on the left side. Must have been a beautiful ride.
    Thanks for your reply Muriel. I fear I have not made myself clear when I talked of the "black level being high". What I should have said is the "lowest part of the histogram is well above black level". As you correctly say, the blacks are too low (non existent).

    Thanks
    Dave

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    Re: Why Is It So ?

    As xpat pointed out, haze is the cause of your "problem" , but I also think you overcorrected, a scene like this would not really have any pure blacks in it.

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    Moderator Dave Humphries's Avatar
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    Re: Why Is It So ?

    Hi Dave,

    I agree with Ted's suggestion as to the cause and also Lennart's that this is a tad overcompensated - there are occasions when a full tonal range is not expected by a viewer. On an image like this, personally I would apply Local Contrast Enhencement first*, say between 5 and 15%, but at the maximum radius allowed and zero threshold, then nudge the levels to get it looking 'right'. Of course 'right' is subjective and you/others may disagree

    * If anyone is wondering why I do it in this order; Local Contrast Enhancement will expand the dynamic range of an image, if you've already set the black and white points as 'tightly' as you screen grab histogram indicates, applying LCE will lose/compress detail in both highlights and lowlights. However, you don't see the histo change when ticking/unticking "Preview" checkbox (in USM dialog), the only way to see the effect in the histogram is to toggle the amount from say 10% back to zero repeatedly (with Preview remaining ticked).

    Cheers,

  8. #8
    dje's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by lenelg View Post
    As xpat pointed out, haze is the cause of your "problem" , but I also think you overcorrected, a scene like this would not really have any pure blacks in it.
    Thanks for your comments Lennart. You've given me something else to think about now !

    Dave

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    Re: Why Is It So ?

    dje,

    I think everyone gave great advice. The idea of using Local Contrast Enhancement to expand the dynamic range is new to me and well worth a try.

    I don't understand your comment about the original being "clearly badly underexposed," as neither the image nor the histogram seems to indicate that. The histogram is fairly well centered. Though it lacks dynamic range, that's the scene that you were capturing, which is very different from being underexposed. If it had been dramatically underexposed, the histogram would have been far more to the left.

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    Re: Why Is It So ?

    I think it is worth separating the problem of haze from low dynamic range. You can have small dynamic range without the haze. The core issue, it seems to me, is that the dynamic range was limited, and the metering method chosen centered the histogram, as evaluative and averaging metering would be expected to do.

    Dave, your suggestion to start with local contrast adjustment is fascinating. I routinely use it do deal with haze, but I never thought about it in terms of dynamic range. I'm going to play with this and compare it to what I normally had done, which was to stretch the histogram first, e.g., with black and white points. Thanks for posting this.

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    Re: Why Is It So ?

    Dave you say you you apply Local Contract to increase the dynamic range, I seem to remember seeing that, however I can not remember where to find it. If you could be so good as to point me in the correct direction.

    Cheers:

    Allan

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    Re: Why Is It So ?

    Quote Originally Posted by Polar01 View Post
    Dave you say you you apply Local Contract to increase the dynamic range, I seem to remember seeing that, however I can not remember where to find it. If you could be so good as to point me in the correct direction.

    Cheers:

    Allan
    One place where LCE it is available is here: http://www.cambridgeincolour.com/tut...nhancement.htm

    Another option is similar to LCE is using Willie Bau's High Contrast and Detail Effect using dodge and burn technique.
    Last edited by FrankMi; 29th July 2012 at 04:12 PM.

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    Moderator Dave Humphries's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by Polar01 View Post
    I can not remember where to find it. If you could be so good as to point me in the correct direction.
    Hi Allan,

    Further to Frank's reply, to actually 'do it', look for Filter > Sharpen > UnSharp Mask (USM) in the Photoshop CS menu, or if you're an Elements user, it is in menu under Enhance > UnSharp Mask.

    Cheers,

  14. #14
    dje's Avatar
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    Re: Why Is It So ?

    Thanks everybody for your comments. This has certainly been very informative for me.

    Dave I will try your LCE suggestion and report back.

    Dave

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    Re: Why Is It So ?

    Dave, I scrolled through your image and thought I recognize that view (Mount Baker) before I read where you'd taken the photo. My wife and I have been doing day driving trips on the island and have been surprised by how much summer haze there has been this year. So I've read with much interest the suggestions for dealing with it.

  16. #16
    dje's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by Cantab View Post
    Dave, I scrolled through your image and thought I recognize that view (Mount Baker) before I read where you'd taken the photo. My wife and I have been doing day driving trips on the island and have been surprised by how much summer haze there has been this year. So I've read with much interest the suggestions for dealing with it.
    Thanks Bruce, that's interesting to know.

    Dave

  17. #17
    dje's Avatar
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    Re: Why Is It So ?

    I had another play with this shot in PS - applied US mask at 15% and max pixel radius and then adjusted levels. The LCE did widen the histogram (but not by a lot) and I applied less correction for the blacks in Levels.

    Another thing that springs to mind with this type of image is that the viewing software and display adjustment could have a fairly noticable effect on the vieiwing experience ?

    Thanks again for all your comments
    Dave

    Why Is It So ?
    Last edited by dje; 30th July 2012 at 02:10 AM.

  18. #18

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    Re: Why Is It So ?

    A really attractive version, Dave. You'll surely want to eliminate the black thing (perhaps a bird) that is in the sky directly above the mountain.

  19. #19
    dje's Avatar
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    Re: Why Is It So ?

    Quote Originally Posted by Mike Buckley View Post
    A really attractive version, Dave. You'll surely want to eliminate the black thing (perhaps a bird) that is in the sky directly above the mountain.
    Thanks Mike. Black spot removed !

    Dave

  20. #20
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    Re: Why Is It So ?

    Dave,

    I think all of the advice has been really good, and I think that your latest edit has turned out perfectly. It captures the light on the mountain, the haze very well.

    -Sonic

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