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Exposure & Histograms

mvheystmvheyst Member
edited August 2011 in general photography
I want to ask questions on this forum regarding Exposure & Histograms. I want to submit histograms of photographs, but I don't know how to get a JPEG file of the histograms. Can anyone provide me with a method to create a JPEG file of a Photograph's Histogram?

Comments

  • I have the following practical problem with "correct exposure":

    When I shoot outdoors (in strong sunlight), it is difficult to see the picture on the camera's screen.

    I can take 2 photographs (with no clipping of shadows or highlights), but the one histogram is more towards the left (darker), and the other histogram is more towards the right (lighter image).

    When I have a scene, I don't know if I should shoot for the lighter or for the darker image. Sometimes the darker image looks better, whilst other times the lighter image looks better.

    The sun may make it hard to judge the appearance of the photographs on the camera screen, and both Histograms may be technically correct, but there may be a large difference in their appearances.

    Question: How do you get optimal / correct exposure, when you don't have any (black or white) clippings?


  • Neil vNNeil vN Administrator
    Do you want the in-camera histogram as a JPG?
    I simply photographed the back of my camera when I had to illustrate this in my book.

    If you want the histogram of the image in Photoshop, then a screengrab of the Photoshop histogram will do it.
  • Thanks Neil, it make sense to photograph the back of the camera. I can do this with newly taken images, but I can't copy and paste a downloaded photograph back on the D300. It would be the ideal to find software that can create a RGB histogram from a JPEG file.

    Some of the questions I wanted to ask is actually answered on this website:

    http://www.scarletuser.com/showthread.php?t=567

    (Picture of the Parrots with the High contrast / Low Contrast Histograms).

    " You always want to aim for the widest possible "Tonal Range" (Contrast) without actually underexposing or overexposing the luma, and/or any of the color channel(s) "

    My problems:
    a) I don't know how to get "the widest possible Tonal Range" in a practical situations.

    b) Look at the 3rd picture from the bottom (city), the " Ideally exposed "Centered Key" Image ". To my eye this image appears to have a slightly "low contrast" appearance.

    Now look at the last picture (Desert). To my eye, the " Ideally exposed "High Key" Image " does not have this "low contrast" appearance.

    I don't have a problem with the contrast of the " Ideally exposed "Low Key" Image " (sunset).

    The Ideally exposed Centered Key image may have a technically correct exposure, but to my eye the low contrast appearance makes it less pleasing to the eye.
    * Is it just a characteristic of a Centered key image, or can you change it ?

    Neil, when I look at the photographs you posted, it doesn't shows this "low contrast" problem.

    How do you practically approach exposure to eliminate the "low contrast" problem?
  • I don't shoot Nikon but wouldn't Capture NX or Capture NX2 have a histogram display?

    If so, that histogram would be the same as the one displayed on the camera's LCD since both histograms will be based on the preview JPEG that is embedded in every Raw file.

    It seems to me that you're over-thinking things. First of all, NEVER use the camera's LCD to assess/judge the exposure of an image. Its best used only to verify that you got the composition you intended. To actually assess your exposure use the histogram; preferably the RGB histogram. Ideally you want your histogram to be weighted to the right, just short of clipping (clipping is indicated in a histogram by a spike at either the Shadow or Highlight ends).

    When shooting Raw its best to Expose to the Right and they make whatever adjustments you need in post production. Its quite simple to use a Raw Converter to maximize the Tonal Range of a photo.

    For the rationale behind Exposing to the Right see: http://www.luminous-landscape.com/tutorials/expose-right.shtml
  • mvheystmvheyst Member
    edited August 2011
    Neil's article: "wedding photography – light & lighting; posing & direction" refer.
    http://neilvn.com/tangents/2011/07/05/wedding-photography-light-posing-direction/

    image

    Neil, do you have the histogram of this image? Did you get any flashing highlights in the white dress of the bride?

    In the situation above, I would have tried (wrongly ?) to expose the background trees correcly (except for maybe blown highlights in the sky), and use flash to try and expose the bride correctly.

    How do you get the bride correctly exposed? You can look for blown highlights on the camera display (blinking highlights), but how do you know the bride isn't under exposed?

    Do you just rely on what you see on the screen of the camera?

    If I put the camera on Manual mode, and use a (Seconic 358) light meter to measure the light at the bride (without flash) (and enter these values into the camera), will the exposure be the same as yours?

    ... or will it work better if I enter a lower light meter reading in the camera (say 1 stop less) to allow the flash to add the additional light?

    For interest sake, the pull back shot Neil used:

    image
  • mvheystmvheyst Member
    edited August 2011
    In this article, Neil didn't follow "the rules". The Histogram of the photograph shows "blown highlights" as the exposure is mostly to the right.

    exposure metering & observing the available light (model: Aleona)

    http://neilvn.com/tangents/2011/08/28/exposure-metering-observing-the-available-light/#more-8995

    image



    Comment by Nancy — August 29, 2011 @ 12:15 am :

    " I’m guessing that your histograms were wildly different for each angle and that blinkies were also different, so I was curious, are you spot metering on her face to get your exposure reading, and if so, is dead center on your camera’s meter (18% gray) the most accurate reading for a model of her skin-tone? "

    How do you ensure the exposure of the subject / model is right?
    Do you rely on i-TTL to get the exposure of the model right?
  • Neil vNNeil vN Administrator
    mvheyst said: do you have the histogram of this image?
    Did you get any flashing highlights in the white dress of the bride?
    No, I don't have the histogram. It would be useless in this instance anyway because of how the over-bright background would spike the histogram on the right-hand side. There's no useful information there.

    Did I get flashing highlights on the bride's dress? Of course not. That would mean over-exposure.
  • Neil vNNeil vN Administrator
    mvheyst said: How do you get the bride correctly exposed?

    You can look for blown highlights on the camera display (blinking highlights), but how do you know the bride isn't under exposed?
    I under-exposed slightly for the bride & bridesmaids, and then let the TTL flash take up the slack.
  • Neil vNNeil vN Administrator
    mvheyst said: Do you just rely on what you see on the screen of the camera?
    A lot. But I am also guided by common sense.
    And blinking highlights. On top of that, I shoot in RAW.

  • Neil vNNeil vN Administrator
    mvheyst said: If I put the camera on Manual mode, and use a (Seconic 358) light meter to measure the light at the bride (without flash) (and enter these values into the camera), will the exposure be the same as yours?

    ... or will it work better if I enter a lower light meter reading in the camera (say 1 stop less) to allow the flash to add the additional light?
    I under-exposed slightly for the bride, and let the TTL flash take care of it.
    This much is clearly stated and explained in the article.


    You're making this too much of an academic exercise.

    There's a specific method here. It works. It gets me the shots, and I can shoot fairly fast, and fluently.
    That's more important than dissecting every choice and every numerical value at the time.

    This also means that it isn't that useful dissecting and analyzing this setup and the method to such a fine degree.

  • Neil vNNeil vN Administrator
    mvheyst said: In this article, Neil didn't follow "the rules".
    What rules?

    I am exposing for my subject. My background's exposure is fairly trivial in this case, because it isn't a specific THING or SUBJECT that I need to expose correctly for.

  • Neil vNNeil vN Administrator
    mvheyst said: Do you rely on i-TTL to get the exposure of the model right?
    Read the text of the article. It's all available light. That's the idea behind the article.
  • Neil vNNeil vN Administrator
    mvheyst said: My problems:
    a) I don't know how to get "the widest possible Tonal Range" in a practical situations.
    1. Shoot. In. RAW. Always. All the time.

    2. Then with your additional lighting (or directing your subject in relation to available light), control the amount of contrast / tonal range of your subject.
  • Neil vNNeil vN Administrator
    mvheyst said: Neil, when I look at the photographs you posted, it doesn't shows this "low contrast" problem.

    How do you practically approach exposure to eliminate the "low contrast" problem?
    1. This ----> Shoot. In. RAW. Always. All the time.

    2. Then with additional lighting (or directing your subject in relation to available light), I can control the amount of contrast / tonal range of your subject.

    3. then, with good initial defauls for my RAW files ..
    http://neilvn.com/tangents/2011/06/19/so-i-shot-in-raw-format-now-what/

    ... and then I edit my RAW files for Contrast, Saturation, Exposure, Black Point, etc etc .. until it looks good.

    And if needed, I can then edit the JPG further for some more "pop"

    http://neilvn.com/tangents/index/digital-imaging/
  • mvheystmvheyst Member
    edited September 2011
    Hi Neil,

    Thanks for the feedback.

    I may write something stupid (due to a lack of knowledge), but when I realised how stupid I was, I can't change, delete or edit my post. At least I am learning. Thanks for the learning opportunity you created with this blog.
  • Neil vNNeil vN Administrator
    No apologies ... this is how we all learn. :)
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