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Thread: Histowhatagrams?

  1. #1
    DDK's Avatar
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    Histowhatagrams?

    Ok, so I've read through the histogram tutorials here and elsewhere and although excellent and full of lots of technical information, I'm still finding it hard to make the connections between the graphs and the information they're conveying and how to interpret and identify problems using a histogram. I'd provide examples of my own photos but I'm just not at that point of readiness (to embarrass myself) yet so they'd basically just be entirely random which would defeat the point of trying to learn from them.

    I realise that what I'm about to ask is probably a lot to ask so I'll understand if I don't get any replies.

    I was hoping that people could post some bad (since good photos are precious and I'd probably not learn as much from good examples) photos they'd taken with accompanying histograms and possibly explain the relationships between the picture and the histogram and what would need to be changed, in camera not in post, in order to take a better (and yes I realise that's subjective but I need to understand the rules before I can break them) picture.

    Umm... yeah... I think that was clear? Was it? Even I'm not sure. Thanks anyway for any historectogramywhatsit advice you can give.

  2. #2
    Brownbear's Avatar
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    Re: Histowhatagrams?

    Hi Djoran,
    I have lots of great examples of bad histograms and will post a few tomorrow.

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    Re: Histowhatagrams?

    Quote Originally Posted by DDK View Post
    I was hoping that people could post some bad (since good photos are precious and I'd probably not learn as much from good examples) photos they'd taken with accompanying histograms and possibly explain the relationships between the picture and the histogram and what would need to be changed, in camera not in post, in order to take a better (and yes I realise that's subjective but I need to understand the rules before I can break them) picture.

    I think that one can learn a great deal from good Photographic examples.

    ***

    I don’t use the Histogram all that much and I use it even less as a tool to then proceed to Chimp.

    But having stated that, I think that to use an Histogram for any useful purpose you need to first understand what the Image is - what is the Photographer's Vision; then secondly you need to understand what the Histogram will look-like: for THAT particular IMAGE.


    There are no BAD Styles of Wine, but yes there are BAD wines: so to establish what wine is BAD you need to first know what each particular Style of Wine is all about.


    +++


    Image #1

    Here the Histogram crawls up the RH Side and the little spike is representative of blown windows and doors in the background – I’d be looking here that there is NOT a big bunching up at the RH side because about half of the scene is in ‘shadow’ by comparison – the point is the Photographer was looking for detail of the interior of the Mosque so this Histogram looks "OK" to me:

    Histowhatagrams?

    ***

    Image #2

    In this shot the Photographer wanted nothing blown out and the whole image erring toward Low Key (emphasising a pensive and reflective tone) the camera angle was manouvereed such that the lighting in the BACKGROUND was a close to black-black as possible – which was nearly achieved.

    So IF this histogram were crawling up the RH side or (as in the above image#1) there were a nice “bump” in the middle of the Histogram, we would expect that the Photographer’s Vision might not be realized:

    Histowhatagrams?

    ***

    Image #3

    On the other hand for this image the Photographer’s vision was an High Key Image (rendering ‘happiness’ and ‘joy’) – so this Histogram is somewhat like a mirror, of the Histogram in Image #2:

    Histowhatagrams?

    ***

    Image #4

    This image, like Image #3 is also made in soft ambient room light - BUT – the Photographer’s vision was to allow the Subjects to speak for themselves and to carry the weight of the that load by their own personalities and the colours.

    So – the camera viewpoint was chosen differently to that in Image #3.

    Whilst there a little MODELLING on the Subject’s faces (especially OoF Woman), the lighting is reasonably flat and even across the scene – EXCEPT for the large window in the background.

    So we would expect a “flat line” Histogram here – and we got it.

    If we had a big bunch in the LH side we’d be thinking “underexpose” – if we got a big bunching at the RH side we’d be thinking “overexposure”:

    Histowhatagrams?



    WW

  4. #4
    DDK's Avatar
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    Re: Histowhatagrams?

    Quote Originally Posted by William W View Post
    But having stated that, I think that to use an Histogram for any useful purpose you need to first understand what the Image is - what is the Photographer's Vision; then secondly you need to understand what the Histogram will look-like: for THAT particular IMAGE.
    Yes, this is exactly the problem I'm having. Your post was very helpful, thank you.

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    William W's Avatar
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    Re: Histowhatagrams?

    You're most welcome.

    WW

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    Re: Histowhatagrams?

    After I read 'Expose for the Right" on Luminous Landscape some years ago I looked and found the histogram in my camera and it was was such a small thing I immediately forgot about it but took the message "Don't blow your highlights" and "You do not have an 's' curve as with film with the safety aspect of compressed highlights and shadows ... but a straight line with no safety ends". A book on Sensitometry was one of my purchases many years ago ... it has gathered dust for several decades now

    I had also been aware that even my simple camera had a great device for warning me of blown highlights called BLINKIES so I can change away from semi-auto A mode to M mode to correct if the highlights were valuable ... often they are not.

    This not to say I ignore histograms completely as when I use the curves tool in my editor it is a great help and guide for a quick adjustment. I don't know if an understanding of the histogram would have helped me in my early days but it is irrelevant to me these days.

    I do remember an early confusion that the gram ilustrates the amount of tone on the scale from black to white rather than an indication of the position in the picture ... so bright white on left of picture shows as a high line on the right of the gram.
    Last edited by jcuknz; 7th June 2013 at 08:30 AM.

  7. #7
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    Re: Histowhatagrams?

    Learning to check my histogram for over/underexposure and clipping has helped me to improve my photos. Here are some examples of histograms, showing underexposure, overexposure, check for tone and clipping.



    Histowhatagrams?


    The bellies of the pelicans are over exposed.


    Histowhatagrams?


    Black/Shadow clipping on black bellied whistling ducks and a heron...


    Histowhatagrams?


    Histowhatagrams?


    I'm still learning so I'm hopeful that someone else will provide an better explanation of these histograms.

  8. #8
    Administrator Manfred M's Avatar
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    Re: Histowhatagrams?

    A histogram, in isolation is not particularly useful. Where it does help is that it allows one to evaluate some “absolute” information about the image that has been captured, but then, as Bill has already stated, you do have to understand the image itself. A lot of people will try to judge correct exposure based on what they see in their viewfinder, but that is not necessarily a good thing to do as the ambient light conditions may result in the image seem to be too light or too dark.

    What it does for the photographer is to provide feedback on the exposure of the image. In an ideal world, we would to not lose shadow detail or have highlights blow out, and the histogram does this for us. A dark image should show up with a lot of data on the left (as per Bill’s low key posting) or in the case of a high key image, the data will be pushed to the right.

    Histowhatagrams?.

    I do glance at my histogram when I start shooting in a new environment just as a double check on my exposure, but I certainly am not a slave to what it reads. The extreme left and extreme right are the areas I do pay attention to, as the histogram can show me where I have lost shadow detail, which I can often live with. The right side is more critical, as it shows where highlights have been clipped, but even here, things have to be taken in context. If I am seeing specular highlights that are clipped in waves on the water, I don’t get too excited about things, but if significant portions of the sky get blown out, I may take corrective action.

  9. #9
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    Re: Histowhatagrams?

    As far as I know, there are only two USEFUL things that can be ascertained from a histogram (I'm referring to the RGB histogram):

    1) the image is over-exposed.

    2) the image is under-exposed.

    If the dark areas of an image are essential, don't let the histogram "go over the left edge".

    If the highlight areas of an image are essential, don't let the histogram "go over the right edge".

    Do not ever worry about the vertical dimensions of the peaks on the histogram -they are of little or no practical use.

    I think Manfred said pretty much the same things.

    If you shoot JPEG, the histogram is very accurate - if you shoot RAW, it is less so, and the camera needs to be set up for the histogram to be useful. The problem with setting up the camera so as to make the histogram useful for RAW shooting is that it affects the JPEG output adversely.

    Do not ever use the LCD as a judge of exposure of an image - except perhaps for the "blinkies" which can be, but aren't necessarily, useful.


    Glenn

  10. #10
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    Re: Histowhatagrams?

    Quote Originally Posted by Glenn NK View Post
    As far as I know, there are only two USEFUL things that can be ascertained from a histogram (I'm referring to the RGB histogram):

    1) the image is over-exposed.

    2) the image is under-exposed....
    I'd posit a third.

    3) you have a high-dynamic range scene that cannot be covered by a single exposure. (i.e., "shoulders" at BOTH left and right ends of the histogram).

    You can then choose which part of the scene is meaningful to you and expose accordingly. Or possibly to go with bracketed exposures for fusing or HDR post-processing techniques.

    The histogram can also help you determine whether you've covered a large dynamic range with bracketed shots by showing whether the peaks on either end are (reasonably) covered to extinction.

    But overall, yes, there is no such thing as a good or bad histogram--it's not like you should be aiming to have a perfectly bell-shaped centered curve every time. I like the demonstration of this on the Luminous Landscape tutorial on histograms. And of course, Levels adjustments are basically manipulating the histogram in post.

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    Re: Histowhatagrams?

    I use the histogram in my camera in difficult situations where I know that I will need to do more than usual post-processing. DSLRs capture much more data in the overexposed area than in the underexposed. So I set the exposure as much to the right as comfortable without blowing the whites. (This may be what jcuknz is referring to.) If you underexpose then lighten in post-processing you can insert more noise. Obviously, a correct exposure is best. In Lightroom I watch the histogram if I want to increase tonality.

    Hopefully someone with more experience can confirm or correct this

  12. #12
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    Re: Histowhatagrams?

    Quote Originally Posted by inkista View Post
    I'd posit a third.

    3) you have a high-dynamic range scene that cannot be covered by a single exposure. (i.e., "shoulders" at BOTH left and right ends of the histogram).

    You can then choose which part of the scene is meaningful to you and expose accordingly. Or possibly to go with bracketed exposures for fusing or HDR post-processing techniques.

    The histogram can also help you determine whether you've covered a large dynamic range with bracketed shots by showing whether the peaks on either end are (reasonably) covered to extinction.

    But overall, yes, there is no such thing as a good or bad histogram--it's not like you should be aiming to have a perfectly bell-shaped centered curve every time. I like the demonstration of this on the Luminous Landscape tutorial on histograms. And of course, Levels adjustments are basically manipulating the histogram in post.
    Kathy:

    OK, I agree with point 3).

    I also agree with what else you said. When we do PP, we are adjusting the histogram, so it will end up looking like what we want and what we need.

    Please people - only look at the ends of the histogram on your LCDs - it's probably going the change in PP anyway.

    Repeat: do not judge exposure or colour of an image by the LCD image. There are some high end bodies, some of which have poor LCDs, and one recent one is reputed to have come out with some copies that have a greenish cast. Good luck with that.

    Glenn

    PS - on Canon bodies, it's often recommended to adjust the Contrast to minus two or three when shooting RAW.
    Last edited by Glenn NK; 7th June 2013 at 10:33 PM.

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    Re: Histowhatagrams?

    Quote Originally Posted by Glenn NK View Post
    . . . on Canon bodies, it's often recommended to adjust the Contrast to minus two or three when shooting RAW.
    You might wish to expand on the reason for recommending this technique: my guess is that many folk will not immediately understand the correlation and the relationship.

    I understand you alluded to the reason in Post #9

    WW

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    Re: Histowhatagrams?

    O/T - Groovy Shot Manfred!

  15. #15
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    Re: Histowhatagrams?

    Quote Originally Posted by William W View Post
    You might wish to expand on the reason for recommending this technique: my guess is that many folk will not immediately understand the correlation and the relationship.

    I understand you alluded to the reason in Post #9

    WW
    William:

    My apologies (and thanks for not quoting the whole post I made - it's just confusing).

    If one shoots RAW, the camera doesn't put out a JPEG image on the CF/SD card, but it does create a JPEG to display on the LCD (RAW not being an image that will display).

    The JPEG image used for the LCD has been processed - including pulling down the exposure level in the highlights so they don't blow out (as badly if such is the case).

    In order to compensate for this, it is frequently recommended on POTN to set the in-camera CONTRAST to minus two or even minus three (I use -3).

    This would get the JPEG to display the highlights more closely to what a converted RAW file would actually deliver when converted in PP. This way, one could get the converted RAW image highlights (the right side) closer to the right when using ETTR (exposing to the right), but without the danger of blowing the highlights out.

    Hope this makes sense.

    If this is true, then it follows that shooting RAW + JPEG poses some problems if one uses ETTR. It seems logical that you can't have both of them ETTR.

    I also believe that this technique applies to all brands of camera, but since I shoot Canon bodies, and have spent considerable time in the past on POTN (a Canon site), I'm not positive about it being applicable to all brands.

    Glenn

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    Re: Histowhatagrams?

    Djoran... Thank you for starting this thread... Great info here.

  17. #17
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    Re: Histowhatagrams?

    Whoops missed this previously.

    Quote Originally Posted by Glenn NK View Post
    Do not ever use the LCD as a judge of exposure of an image - except perhaps for the "blinkies" which can be, but aren't necessarily, useful.
    Actually, the blinkies can also be misleading.

    Better explanations here: http://www.brisk.org.uk/photog/hiblow1.html

  18. #18
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    Re: Histowhatagrams?

    Quote Originally Posted by inkista View Post
    Whoops missed this previously.



    Actually, the blinkies can also be misleading.

    Better explanations here: http://www.brisk.org.uk/photog/hiblow1.html

    Yes, that's why I said "can also be misleading".

    I've experienced just what the article noted with my 5DII.

    Maybe the "blinkies" are generated from the JPEG (RAW files wouldn't be of much use here), and if so, then the blinkies are about as useful as a JPEG in judging a RAW file.

    But I have found that when the whole sky is blinking on the LCD, the RAW file converted has little or no detail in the sky.

    Glenn

  19. #19
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    Re: Histowhatagrams?

    Quote Originally Posted by Glenn NK View Post
    Yes, that's why I said "can also be misleading".

    I've experienced just what the article noted with my 5DII.

    Maybe the "blinkies" are generated from the JPEG (RAW files wouldn't be of much use here), and if so, then the blinkies are about as useful as a JPEG in judging a RAW file.

    But I have found that when the whole sky is blinking on the LCD, the RAW file converted has little or no detail in the sky.

    Glenn
    Kathy and Glenn, thank you for raising this issue with blinkies. I use a Canon 60D but assume precisely the same issue applies as with the 5D test on the link posted by Kathy.

  20. #20

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    Re: Histowhatagrams?

    Quote Originally Posted by William W View Post
    I think that one can learn a great deal from good Photographic examples.

    ***

    I don’t use the Histogram all that much and I use it even less as a tool to then proceed to Chimp.

    But having stated that, I think that to use an Histogram for any useful purpose you need to first understand what the Image is - what is the Photographer's Vision; then secondly you need to understand what the Histogram will look-like: for THAT particular IMAGE.


    There are no BAD Styles of Wine, but yes there are BAD wines: so to establish what wine is BAD you need to first know what each particular Style of Wine is all about.

    +++

    Image #1

    Here the Histogram crawls up the RH Side and the little spike is representative of blown windows and doors in the background – I’d be looking here that there is NOT a big bunching up at the RH side because about half of the scene is in ‘shadow’ by comparison – the point is the Photographer was looking for detail of the interior of the Mosque so this Histogram looks "OK" to me:

    Histowhatagrams?

    ***

    Image #2

    In this shot the Photographer wanted nothing blown out and the whole image erring toward Low Key (emphasising a pensive and reflective tone) the camera angle was manouvereed such that the lighting in the BACKGROUND was a close to black-black as possible – which was nearly achieved.

    So IF this histogram were crawling up the RH side or (as in the above image#1) there were a nice “bump” in the middle of the Histogram, we would expect that the Photographer’s Vision might not be realized:

    Histowhatagrams?

    ***

    Image #3

    On the other hand for this image the Photographer’s vision was an High Key Image (rendering ‘happiness’ and ‘joy’) – so this Histogram is somewhat like a mirror, of the Histogram in Image #2:

    Histowhatagrams?

    ***

    Image #4

    This image, like Image #3 is also made in soft ambient room light - BUT – the Photographer’s vision was to allow the Subjects to speak for themselves and to carry the weight of the that load by their own personalities and the colours.

    So – the camera viewpoint was chosen differently to that in Image #3.

    Whilst there a little MODELLING on the Subject’s faces (especially OoF Woman), the lighting is reasonably flat and even across the scene – EXCEPT for the large window in the background.

    So we would expect a “flat line” Histogram here – and we got it.

    If we had a big bunch in the LH side we’d be thinking “underexpose” – if we got a big bunching at the RH side we’d be thinking “overexposure”:

    Histowhatagrams?

    WW
    Hi Christina,

    I guess we have a lot to thank Bill and Manfred for their very informative posts. What makes them easy to grasp is because of the sample photos showing what they mean.

    First time I realized histograms can be indicative of the "mood" conveyed by the images. Like to the left , equates to moody; while, to the right, to happiness , upbeat mood.

    Like in music. The minor chords, the "sadness" side, and the major chords, the "happy, joyous" side.
    Last edited by nimitzbenedicto; 8th June 2013 at 07:58 PM.

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