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Thread: Histogram question

  1. #1

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    Histogram question

    A histogram that shows BOTH blacks and whites extending (respectively) beyond black point and white point is indicative of what?

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    Re: Histogram question

    This shows both black shadows (without detail) and clipped highlights. It means the dynamic range of the scene extended that of your sensor at that particular ISO. It is left to your interpretation how adverse this is: are the clipped highlights just due to the sun or a light source in the picture which should anyway be white, do you want detail in that shadow where there are none? Are the clipped highlights only of one channel or of all three (a picture of a bunch of red roses easily produced some clipped reds)?

    Just to mention it: If you shoot raw, it pays to see whether you can retrieve some highlights of shadows not only by moving the shadow and highlight sliders, but also the exposure slider.

    Lukas

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    Re: Histogram question

    Now I can't recall where the photo is (I have eight terabytes here) but it looks quite good despite the histogram. So, the dynamic range of the scene was a little too much for the sensor. I get that. Perhaps three photos -1/2 EV, EV, +1/2 EV and made into a HDR photo would reveal more tones. As to the esthetics, that's another point.

  4. #4

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    Re: Histogram question

    Histogram question
    OK, here we go. I imagine the individual color channels could be adjusted here.

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    Re: Histogram question

    Quote Originally Posted by Abitconfused View Post
    Perhaps three photos -1/2 EV, EV, +1/2 EV and made into a HDR photo would reveal more tones.
    No. .5EV will do approx nothing. If you're going to construct an HDR photo, shoot at a minimum of 2EV steps.

    Keep in mind that the histogram you have is the result of adjustments that you've already made and keep in mind too that there's no ideal histogram; in my opinion, you probably want less detail in this shot, not more (the midtones are looking quite washed out in places.

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    Re: Histogram question

    Quote Originally Posted by lukaswerth View Post
    It means the dynamic range of the scene extended that of your sensor at that particular ISO. I
    Not necessarily; it just means that that's the current state of the image -- which isn't necessarily how it was when it was captured.

  7. #7

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    Re: Histogram question

    Grab a cuppa and watch this...http://www.youtube.com/watch?v=EjPsP4HhHhE

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    Re: Histogram question

    Quote Originally Posted by chauncey View Post
    Grab a cuppa and watch this...http://www.youtube.com/watch?v=EjPsP4HhHhE
    Thanks for this William, I will learn from watching this one too...I'll find a time for me.

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    Irene Eva

    Re: Histogram question

    Thanks for the link. I'll make it a point to watch this as well.

    Irene

  10. #10
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    Re: Histogram question

    Ed sometimes when you have black or white clipping it can be useful to turn on the exposure "blinkies" in the editing software you are using. This shows the areas of the image where clipping is occurring with a colour overlay or perhaps flashing light.

    In your image, the black clipping is probably occuring in that dark area under the bridge and the white clipping may be some highlights on the bridge itself or the bridge in the background. And as Colin says, they may have been caused or exaggerated by the editing adjustments.

    Dave

  11. #11
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    Re: Histogram question

    Quote Originally Posted by Colin Southern View Post
    Not necessarily; it just means that that's the current state of the image -- which isn't necessarily how it was when it was captured.
    To add to this: that's why it is helpful to check the histogram on the camera if you think your scene may have more dynamic range than the sensor can handle. Since the histogram reflects a jpeg thumbnail, you can make it more accurate by picking a very neutral picture style.

  12. #12

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    Re: Histogram question

    Quote Originally Posted by DanK View Post
    To add to this: that's why it is helpful to check the histogram on the camera if you think your scene may have more dynamic range than the sensor can handle. Since the histogram reflects a jpeg thumbnail, you can make it more accurate by picking a very neutral picture style.
    +1

    I might add too through that although the in-camera histogram is based on a JPEG - and is thus conservative - that "conservativeness" (is that a real word?) equates to "safety margin". Most composite histograms won't indicate a single channel over-exposure - and in certain types of shots (eg very warm sunsets) you're likely to blow one channel long before others.

    At the shadow end it's even more conservative - usually with a RAW capture you can dig quite a bit more out of the shot, although it may get noisy if pushed too far.

  13. #13

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    Re: Histogram question

    Quote Originally Posted by lukaswerth View Post
    Just to mention it: If you shoot raw, it pays to see whether you can retrieve some highlights of shadows not only by moving the shadow and highlight sliders, but also the exposure slider.
    Ed,

    If you're serious about knowing the true exposure of the sensor in your shot, I would heartily recommend a utility called RawDigger which can show you a histogram of all four raw channels R,G,B,G1. Since the histogram is of the actual raw data you can easily see if the sensor itself was saturated by the exposure and therefore has unrecoverable highlights. I find this a better starting point rather than trying to guess what the raw converter did to my image.

    A case in point is IR imaging (OT for most folks) with my Sigma SD10 DSLR. Usually, RawDigger shows no blown highlights in my raw data (I tend to under-expose for IR). When I look at the Review image in SPP's histogram, the green is totally killed *** making the image a horrible purplish-red, as one would expect, with a lot of blown reds. Point here is that the review image is completely unrepresentative of the raw data - also as one would expect; after all, it has just been converted!

    *** my Foveon sensor does respond to near IR in all three layers (channels), approximately in the RGB ratio 6:2:1.

    RawDigger is also good for sorting through bracketed shots, to know for sure which ones to reject.

    Eric
    Last edited by fenix; 6th August 2014 at 04:35 PM.

  14. #14

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    Re: Histogram question

    Quote Originally Posted by DanK View Post
    To add to this: that's why it is helpful to check the histogram on the camera if you think your scene may have more dynamic range than the sensor can handle. Since the histogram reflects a jpeg thumbnail, you can make it more accurate by picking a very neutral picture style.
    To get even closer to raw on the in-camera histogram, one can set a custom in-camera WB to UNIWB. Not a procedure for the faint-hearted and one could be forgiven for being a bit confused ;-)

    But the prize is being able to almost believe the in-camera histogram and thereby approach the grail of ETTR.

    UNIWB . . . don't leave home without it.

    Eric

  15. #15
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    Re: Histogram question

    Mostly I only pay attention to the individual RGB histograms. And as Colin has aptly pointed out, the Histogram is based on a JPEG so if one is shooting RAW, there is a bit more leeway (more conservative) than with JPEG shooting.

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