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How to read the histogram

Discussion in 'Sony Alpha E-Mount Cameras' started by alaios, Apr 1, 2013.

  1. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    Dear all,
    I would like to ask you if you have any guide that can help me understand how to read the live histogram that appears on my camera.
    There have been some times that my camera was reporting everything around the center value but at the same time that was cropped. There was no visible peak so I wonder if that was a 'good" or bad sign. It would be good though to read something even more informative for all possible cases one would face, and how should react.

    R.
    A.
     
  2. gio

    gio TalkEmount Veteran

    382
    Sep 12, 2012
    Manchester, uk
    try this

    [video=youtube;rF_Lg3BlQfs]https://www.youtube.com/watch?v=rF_Lg3BlQfs[/video]
     
  3. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex

    Thanks I have checked the video. I do not understand though

    a. How clipped values affect me? For example all values concetrated around the mean but with no visible peak. How that affects my image?

    b. If all the exposures might be right based on what I need to show (as he says at the end), how I can decide what I need? What is in your brain cells when looking at an image and thinking on how the exposure will affect what you see?

    Regards
    Alex
     
  4. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    Reading the histogram is an art. What it basically tells is how many pixels with certain intensity there are. If the object is dark or there are lots of dark areas (like night photo) the histogram should peak in the start. If the object is very bright the histogram should peak in the end. If there are lots of dark and bright areas but not much between them (like night photo with bright street lamps) there should be two peaks, one in start and one in end.

    With normal (where intensities are divided statistically or about so and colors are average) the location of peak depends about artistic things. Correct exposure don't produce always best photographs.

    The problem with automatic exposure is that camera has no way to know what kind of image you want to create. For example in a darkish room the camera tries to make an averagely exposed photograph. You may want to have darkish image with some parts "correctly" exposed or averagely exposed image where those same parts are overexposed.

    Don't worry too much. Exposure can be adjusted in post processing (especially if shooting raw). Same holds true with contrast and white balance.
     
  5. dbmiller

    dbmiller TalkEmount Top Veteran

    777
    Mar 2, 2012
    New England
    That may be true, but if the histogram shows everything squished to an edge, there may not be enough detail to recover. So paying attention to the history will at least help you take a picture that you can process from the information that was captured. As opposed to blown out highlights or overly dark shadows that you can't do anything with.

    There's also the whole group of "Expose to the right" theorists. Where even in a dark scene, you push the histogram as far right as you can for capture, then take it back to darkness in post to get "more shadow detail".
     
  6. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    That is at least theoretically way to do (that is, overexpose) if you can. If there isn't blown out highlights you can recover the image in post processing and reduce the noise too. Unfortunately this is just theory. Usually when you need high iso you can't overexpose (you need the speed and can't make aperture larger) and when you can there usually is some bright object that will be blown away.

    I usually have exposure compensation set to +1, works for me. With manual settings it is the histogram and attitude not too much right or left and I try to take lightness/darkness of object into consideration too. Error of +-1 EV don't really matter but usually it is better to err in high side.
     
  7. Jaf-Photo

    Jaf-Photo TalkEmount Veteran

    484
    Mar 25, 2013
    I think that if you are fairly new to shooting, it is enough to check the histogram to make sure that it doesn't peak too heavily to one side or the other. The same applies when you are editing photos afterwards.

    As you develop your own taste in photography, you can use exposure more and more deliberately.

    Rather than over-exposing photos, which I don't like, you can under-expose them. This will allow lower ISO settings or faster shutter speeds, to counter noise or shake. Then you can easily up the exposure in post processing. One advantage of this method is that you will normally keep more detail in the highlights, which the eye is more interested in than the shadows.
     
  8. xXx1

    xXx1 TalkEmount All-Pro

    Jan 15, 2013
    That is true too. Unfortunately there are no fast rules here. Too much overexposing is especially bad if one shoots jpeg and this overexposing thing comes only from the fact that sensor has got 12-14 bits per color and if you can keep the exposure such that nothing is blown away but upper end of bits is used you can lessen noise in post processing adjusting the exposure down. Most of times in this kind of situation you are using low iso so there is no need for noise reduction anyway.

    I think that histogram is a great tool but lots of great photos have been taken without it. Great photos have bee taken without exposure metering too.
     
  9. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    Thanks, I mostly liked the background info I got from you. I hope you have also some more discussion on other places like websites or forums so I can keep reading :)