Results 1 to 3 of 3

Thread: Histogram. RGB or Luminosity ?

  1. #1
    Senior Member brianw999's Avatar
    Join Date
    May 2006
    Location
    Tunbridge Wells, Kent. UK.
    Posts
    11,863

    Default Histogram. RGB or Luminosity ?

    I'm not going to reinvent the wheel here because there are others who have written far more detailed explanations than me. This link takes you to an excellent comparison between the RGB Histogram and the Luminosity Histogram.....

    http://www.workshopsforphotographers...ding-histogram

    In Photoshop CS, when you are adjusting the histogram for brightness and contrast (and you will often see a comment in the forum or in a rejection to "check and adjust the luminosity histogram" when you get a Dark/Under and/or Contrast rejection, especially from me) then you should be using the luminosity histogram rather than the default RGB histogram that you see when you go to Image....Adjustments....Levels .

    ......................................

    The luminosity histogram can be found in "Window....Histogram". Select this option and park it in a corner of the screen. Click the middle tab named Histogram and using the drop down find and select Luminosity.
    You cannot work directly on this histogram.....

    ...so now you need to go to "Image....Adjustments....Levels" where you can make adjustments. Make sure that you have RGB selected here. You will see three arrows on the baseline of the graph. The left side arrow adjusts the dark tones, the middle arrow adjusts the midtones and the right arrow adjusts the highlights.

    You might also see that the two graphs are a different shape and may well have different gaps at each end. These gaps indicate missing dark and light tones depending on which end of the graph they are at. You need to drag the relevant arrow in to touch the graph where it meets the baseline. Make the adjustments on the RGB graph but watch the effect on the Luminosity graph. Setting the left and right side of the luminosity histogram will set optimum contrast. You may have to adjust the midtones as well especially if you have deep shadows or bright highlights but this is a personal judgement for you to make.

    So, remember, when you process use the Luminosity Histogram to set optimum brightness and contrast.
    Last edited by brianw999; 10-29-2014 at 08:37 PM.
    If it 'ain't broken........ Don't try to mend it !


  2. #2
    Junior Member
    Join Date
    Apr 2004
    Posts
    53

    Default

    Hi Brian

    This site would be really helpful, but unfortunately the link is now broken. Are you able to recommend another site?

    Cheers
    Mark

  3. #3
    Member
    Join Date
    Jun 2017
    Location
    KLAS
    Posts
    117

    Default

    Quote Originally Posted by mtaylor334 View Post
    Hi Brian

    This site would be really helpful, but unfortunately the link is now broken. Are you able to recommend another site?

    Cheers
    Mark
    I know it's been a while since you asked lol, but for future info, try this link:

    https://web.archive.org/web/20160430...ding-histogram

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •