histogram how to
  • sclater29
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    histogram how to

    by sclater29 » Mon Oct 31, 2011 2:33 am

    hi all , i have some questions about histograms, my very very limited knowledge tells me that when you review a photo you should have a nice round hill shape that should mean the photo is shot properly exposed

    secondly i understand that if the histogram is to the left it indicated underexposure and to the right over exposure and this is where my knoweledge stops,

    1.if you shot a photo and it has a "perfect histogram" does that mean the photo is perfect or does it need post processing , how important is the histogram to the photo

    2.when post processing i understand that you should use your histogram and edit to your artisic intention however if you histogram is all over the place if you edit the photo to make the best histogram is that the better way to edit?

    3. i want to more a bit more about the technical side of histograms for example if you have a histogram that is say two hills with a valley between them what does that mean and how do you correct it (my guess it means its to overexposed and underexposed at the same time?)

    any help or pictures would be greatly appreciated
    canon 5Dmk2, EF24-105L IS USM,Ef16-35 f2.8L II USM,Ef 70-300 f4-5.6L IS USM, photo shop cs5, photomatix.http://www.flickr.com/photos/sclater29/
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    by Busiboy » Mon Oct 31, 2011 5:17 am

    There is general such thing as a perfect histogram or a curve of what a histogram should look like.

    A histogram just is.

    What I gather from histogram is if the shot is I've or under exposed or if there is any leeway in the shot to push one way or another.
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    by W G » Mon Oct 31, 2011 6:52 am

    sclater29,

    Myths and fallacies abound regarding histograms - especially histograms displayed on the camera.

    The shape of the curve (and the number of hills and valleys) will depend entirely upon the image content and the tonal distribution of the scene.

    The main thing is to ensure that all the peaks and troughs are within the limits of the histogram and that areas of bright or dark do not 'CLIP' by running off the graph.

    Many suggest 'exposing to the right' which means keeping the curve to the right hand side of the graph thus ensuring that the dark values avoid noise by getting too far to the left. These days the noise characteristics of digital devices are much better and so this is somewhat 'old news'.

    What is called for is GOOD EXPOSURE where all of the data in the scene is faithfully recorded in the file to be interpreted to taste later.

    In the days of film it was said that the NEGATIVE is the musical score and the PRINT is the performance. The same holds true in digital — get all the information into the file and them manipulate that information to express your narrative or sensitivity to what you shot.

    Cheers,
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    "Photography was not a bastard left by science on the doorstep of art, but a legitimate child of the Western pictorial tradition." —Robert Galassi
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    JazzXP
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    by JazzXP » Mon Oct 31, 2011 8:21 am

    The histogram is just a guide. I mainly use it to see if I'm blowing out highlights (or underexposing) along with checking the individual channels to see if one of those is blown (red usually goes first, and won't show up on the blinkies unless the overall exposure is blown).

    As for shape, yep, that bell curve around the middle is ideal, but don't rely on that, it's very dependant on what you're shooting, and can be misleading (I've had what looked like a perfect exposure on the histogram turn out to be about a stop underexposed on the subject I want).
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    Dug
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    by Dug » Mon Oct 31, 2011 6:27 pm

    Remember your camera light meter still sees the entire world as an 18% grey. Set your camera first set your camera on manual, take a meter reading off something that is 18% grey ( your classic grey card or a piece of mid range coloured cloth should do ) keep the exposure and photograph something totally black under the same light and something totally white.

    Then set the meter to P or Auto and photograph the 3 subjects using that under the same light.

    Under P or Auto the camera will turn everything to the same shade of grey.


    Also remember you can still adjust this in levels after the shot to a great extent
    . :D

    I must remember to take some photos to explain this

    It is quite fascinating :lol:
    "Photography to the amateur is recreation, to the professional it is work, and hard work too, no matter how pleasurable it may be."

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    ( Total NIKON bigot )

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    by Ken182 » Thu Nov 10, 2011 4:17 am

    http://www.luminous-landscape.com/tutor ... rams.shtml

    The Luminous Landscape has many truths in it
    In a forum, no one can hear you scream!

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