14 Replies Latest reply on Nov 1, 2011 4:08 PM by areohbee

    Basic histogram questions

    media kat Level 1

      I'm looking at the histogram for an image, and it is severely lacking on the right hand side.

      1. Is the right way to describe this histogram is that the light values are clipped?

      2. I know that there is no right or wrog histogram, though how do I use what I see with all the different colors to adjust my image? Can someone without a good eye like me use the histogram to fix the image just based on the histogram alone?

       

      Thanks in advance.

        • 1. Re: Basic histogram questions
          Jeff Schewe Level 5

          media kat wrote:

           

          Can someone without a good eye like me use the histogram to fix the image just based on the histogram alone?

           

          A histogram can tell you certain things...you indication in #1 says the image is under exposed so you'll want to increase Exposure in ACR. But a histogram won't tell you much about color. You would be better off developing your eye...

          1 person found this helpful
          • 2. Re: Basic histogram questions
            media kat Level 1

            1. So will the histogram pretty much just tell if an image is under exposed or over exposed? What else can be interpreted from it?

             

            2. What is the point of seeing the different colors within the histogram if it won't tell much about color?

             

            Thanks.

            • 3. Re: Basic histogram questions
              Jeff Schewe Level 5

              1 yes it tells you the distribution of the levels which can tell you what sort of tone adjustments you might need.

               

              2 it tells you the distribution of the levels in the image which doesn't tell you a lot about color adjustments you might need to make...

              1 person found this helpful
              • 4. Re: Basic histogram questions
                media kat Level 1

                Sorry, for clarification, how do I interpret a histogram such at the attached? Besides being under exposed, what can I interpret from the distribution of colors?

                 

                Thanks!Screen shot 2011-10-31 at 11.59.13 PM.png

                • 5. Re: Basic histogram questions
                  Level 4

                  Kat,

                   

                  That image is absolutely NOT underexposed.

                   

                  That histogram tells you that with even a minute amount of greater exposure, that image will be overexposed, blown, clipped, ruined.

                   

                  You may get away with adding a bit of brightness with the Brightness slider, depending on the image itself.

                   

                  By itself, the histogram is utterly meaningless.  You should have posted the image itself.

                   

                  That histogram might tell me (if I were one to rely on histograms, which I am not) that I should perhaps explore using some Fill Light adjustment to open up the clipped blacks a bit; but I'm pretty sure that would be obvious to me just by looking at the image itself, without any need to look at the histogram.

                   

                   

                  ____________

                  Wo Tai Lao Le

                  我太老了

                  • 6. Re: Basic histogram questions
                    Level 4

                    Oh, the "distribution of colors" tells you nothing at this stage. 

                    • 7. Re: Basic histogram questions
                      media kat Level 1

                      Thanks for your replies Tai Lao.

                       

                      At what point do the distribution of colors come into play?

                      • 8. Re: Basic histogram questions
                        Level 4

                        media kat wrote:

                         

                        …At what point do the distribution of colors come into play?

                         

                        As far as I'm concerned, never.  It is what is. 

                         

                        Looking at the individual channel might tell you if there's enough headroom to increase the saturation of a given color, for instance.  But, again, one doesn't need a histogram to determine that. 

                         

                         

                        ____________

                        Wo Tai Lao Le

                        我太老了

                         

                        Message was edited by: Tai Lao

                        • 9. Re: Basic histogram questions
                          areohbee Level 5

                          Histogram is a tool to be used in conjunction with an image - not out of context / in a vacuum.

                           

                          Some images look best with some clippage at one or both ends, some may look better with the whole mess clustered in the middle. Some may look better with lumps here or there, some a more even distribution.

                           

                          HIstogram helps you understand what you see, and helps give a clue what to do to accomplish a goal, and provides feedback how various adjustments have affected the image "mathematically"......

                           

                          Bottom line is how it looks.

                           

                          Histogram is information. It may or may not be useful when editing a particular image... Partly it may help you in the future to know what adjustment to make depending on situation. For example - brightness vs. exposure - once you see the difference in how exposure affects the histogram vs. brightness, it may help you to know which to use on the next image...

                          • 10. Re: Basic histogram questions
                            areohbee Level 5

                            media kat wrote:

                             

                            At what point do the distribution of colors come into play?

                             

                            When Adobe adds the ability to independently adjust the R, G, & B channels.

                             

                            In the mean time, it is information to help you understand what you see - how that info is to be used, or whether it is useful for you, for a particular image, I can't say...

                             

                            I'm a histogram junkie - I can't help it, I love it. - some people collapse them and never look back. What kind of person are you???

                            • 12. Re: Basic histogram questions
                              areohbee Level 5

                              media kat wrote:

                               

                              ...how do I interpret a histogram such at the attached? Besides being under exposed, what can I interpret from the distribution of colors?

                               

                              Screen shot 2011-10-31 at 11.59.13 PM.png

                               

                              This image could be over-exposed if it really needs to have more shadows and dark tones and no highlights.

                              This image could be under-exposed if it really needs to be brighter, even to the point of clipping some of the highlights...

                               

                              I assume you get by now - it depends on the image itself, and your artistic objectives for the image.

                               

                              Color distribution *could* be semi-useful.

                               

                              It shows that you could increase blacks and only clip the blue channel. If there is blue to spare in the bottom end, this may be a good thing.

                              It shows the reds are the brightest colors, so those will be the ones to suffer first if exposure is increased, although that may be exactly what you want if the reds should be very bright or clipped......, or conversely, if the reds are already over bright, you may want do decrease exposure. It also shows that another way to deal with overblue shadows might be to increase luminance of the blues, if the midtones could use a little more blue too. Maybe you could increase exposure of the whole thing but reduce luminance of the reds - but that would increase the amount of red in the mids and shadows - maybe good, maybe bad.

                              It shows that if the highlights are looking a little too red and the shadows a little blueish, that split toning with anti-blue in the bottom and anti-red in the top might help.

                               

                              All of this could also be gleaned by eye - again, its info to help confirm or explain what you see, or aid with what you are trying to do, once you learn to interpret it, and if you like to work that way...

                               

                              Rob

                              • 13. Re: Basic histogram questions
                                Noel Carboni Level 7

                                media kat wrote:

                                 


                                What can I interpret from the distribution of colors?

                                 

                                Thanks!Screen shot 2011-10-31 at 11.59.13 PM.png

                                 

                                The biggest thing this histogram says to me is that you have channel clipping in the dark parts.  Note how some of the data climbs the left edge.

                                 

                                This may be because you're converting directly to a small-gamut color space, such as sRGB, or because you have the "Blacks" setting up too high.

                                 

                                -Noel

                                • 14. Re: Basic histogram questions
                                  areohbee Level 5

                                  media kat wrote:

                                   

                                  Can someone without a good eye like me use the histogram to fix the image just based on the histogram alone?

                                   

                                   

                                  ACR's auto-tone feature "fixes" images based on histogram alone. But one must ultimately develop one's eyes or post-processing will never be much fun... Auto-toned photos nearly always need additional tweaking for optimal results, sometimes a little, sometimes a lot. Clipping is not evil - it may be the best thing for a photo... - depends on the objective - want silouette? - clip shadows; got specular highlights? - don't try to recover... Many auto-toning algorithms actually default to a modicum of clippage. Likewise, one may not want the histogram to go anywhere near the endpoints of the spectrum - if the photo is of something that really doesn't have any shadows or highlights...

                                   

                                  Summary: This histogram should be used to augment what you see and help you accomplish your objective, not be a substitute for "bad eyes".