Histogram

Discussion in 'Beyond the Basics' started by rmh159, Jul 19, 2007.

  1. rmh159

    rmh159 TPF Noob!

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    We all know that if the graph on the histogram falls off to the right or left it means a loss of detail in whites or blacks but what if it falls off the top? That might be a newb-ish question but I've always wondered if that should interpreted anyway.
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That just means there are more pixels of that tone than others...no loss of detail.

    The histogram is just a visual representation of the actual number of pixels and their tonal value. If there is an overwhelming number of pixels with a mid tone...the histogram will probably show those tones as a tower on the graph. Try shooting a clear blue sky.
     
  3. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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  4. The_Traveler

    The_Traveler Completely Counter-dependent Supporting Member

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    I don't understand what this means. Can you post a picture that had a histogram that falls off the top?
     
  5. rmh159

    rmh159 TPF Noob!

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    Unfortunately, I can't post a pic of what I'm trying to describe.

    If you imagine a bell curve on a histogram but with all of the data crunched into a small area on the X axis to the point where the peak is off of the histogram... so it's more of a spike than a curve but you can't see the top. Make more sense?

    I suspected it wasn't a loss of data but wanted to be sure. One of those simple nagging things that I should've known by now. :)
     
  6. ANDS!

    ANDS! No longer a newbie, moving up!

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    He's just saying that the graph shoots up to the top in one range from black to white. That should be fine, as someone said, just means there are more pixels of that range compared to others. If you took a picture of the sky as suggested, with nothing else in it - youd no doubt get what you're describing. No loss of information, just an overabundance of a single type (or group of similar tone).
     
  7. The_Traveler

    The_Traveler Completely Counter-dependent Supporting Member

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    If you mean a histo like the one below, the values in the middle aren't off the graph. The histo function automatically scales the graph so that the values with the greatest number of pixels are close to or at the top.

    What this histo would mean is that a lot of the middle values have most of the pixels.

    [​IMG]
     
  8. Garbz

    Garbz No longer a newbie, moving up!

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    Within reason. If you put enough tones at one area it will just clip the top off in the preview so you still get some meaningful information out of it. The histogram is useless if it's scaled so you can't see the minor data either. The bottom is what's important as it show "detail" of the image tones if you can roughly understand my poor analogy, it doesn't matter if it is off the top of the scale.
     

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