11 Replies Latest reply on Jul 28, 2011 5:42 AM by lasvideo

    RGB Parade vs YC Waveform

    Sengstack Level 1

      I am trying to figure out what values the RGB Parade Scope displays and how to put those values to best use.

       

      As I understand it, the YC Waveform scope (with Chroma turned off) displays luminance as an IRE value. That's a calculated value, based on human visual perception, as opposed to luma, which is a numerical value within the video signal. That explains why the YC Vectorscope display for the RGB gradients below shows the highest luminance for the green bar, less for red, and much less for blue (the Saturation and Brightness for all the bars were set to 100/100 with opacity for the bottom of the bar set to zero). Those readings make sense because our eyes perceive green as brighter than red, and significantly brighter than blue.

       

      So, what then is being displayed in the RGB Parade scope? For the same RGB gradients, tt is shows values from 0 to 100. If that is IRE, then it does not match the YC Waveform scope. My guess is that it is the B (Brightness) value in the HSB representation of RGB values of the color channel (which matches the values I used when I created the RGB gradient). It is not the L (Lightness) value in the HSL.

       

      If it is the B value in HSB...then the values shown are not luminance, therefore do not represent what the viewer will perceive. As a result, I think using the RGB Parade as a guide when removing a color cast or balancing luminance among the color channels, is ineffective and perhaps even counter-productive.

       

      With that in mind, what is the best use for the RBG Parade and what is the appropriate way to use it.

       

      Jeff Sengstack

       

       

      RGB gradients.jpg

      YC Waveform.jpg

      RGB Parade.jpg

        • 1. Re: RGB Parade vs YC Waveform
          lasvideo Level 4

          I use RGB Parade (whose display allows me to see then adjust  the Black/Gamma/Luma levels with CC software) a lot for color correction. Especially if the color balance is off and needs fixing. Its the first thing I do before any of the other color corrrection processes. I would refer you to the myriad of tutorials on the web that delve deeper then this superficial explanation.

          • 2. Re: RGB Parade vs YC Waveform
            Sengstack Level 1

            The thing is, knowing that the RGB Parade measures Brightness for each color rather than luminance, I don't think it's as helpful a tool as the YC Waveform. Especially since the YC Waveform shows luminance (perceived brightness) for all color channels combined and is an easy way to get feedback as you adjust Shadows/Midtones/Highlights using tools like the levels-style sliders in the Fast Color Corrector or the Three-way Color Corrector.

             

            As for adjusting the color balance, I'm not convinced the RGB Parade gives an accurate reading on how color looks to the viewer. That's because it measures Brightness rather than luminance. I think the Vectorscope is the best means to check on a color cast.

            • 3. Re: RGB Parade vs YC Waveform
              lasvideo Level 4

              You are entitled to your opinion, I just know what I have learned from professional colorists. Its a combination of using the scopes (whatever your preference) and the engineering monitor .Steve Hullfish has this observation ( in the sidebar ) about the role of RGB Parade....

               

              http://books.google.com/books?id=w_NCWL4aJm8C&lpg=PA9&ots=mFyOFWHlJs&dq=rgb%20parade%20def inition&pg=PA9#v=onepage&q=rgb%20parade%20definition&f=false

               

              YMMV

              • 4. Re: RGB Parade vs YC Waveform
                Sengstack Level 1

                I agree that Steve Hullfish is an expert. He notes in that sidebar that each color cell in the RGB Parade "is essentially identical to the regular display of information on a waveform monitor, except that the values only pertain to the amount of that one color in the image."

                 

                What I'm seeing in the P Pro RGB Parade is that the YC Waveform and the RGB Parade scopes are not "essentially identical" (as demonstrated with the screen shots in the original posting).

                 

                I return to my original viewpoint: What does the RGB Parade display? I think it's the Brightness value from the HSB values that are calculated from RGB. The P Pro Help file and Hullfish say it displays the "levels" of the RGB channels. On the other hand the YC Waveform displays Luminance. They are two different animals.

                 

                What would be good is if someone from Adobe would clarify this.

                • 5. Re: RGB Parade vs YC Waveform
                  lasvideo Level 4

                  I think you are getting lost in semantics and theory, which is fine if that makes you happy  ;-)  . Regardless of the theory behind their functions, I find RGB Parade an effective tool when trying to get inital black and white and gamma levels set. It also aids in correcting color balance issues. Thats good enough for me .

                  • 6. Re: RGB Parade vs YC Waveform
                    SteveHoeg Adobe Employee

                    The YC waveforms display luma, not luminance. The observation that the waveforms show highest intensity in the green area would be true for both luma and luminance. The RGB parade isn't showing brightness, luminance or luma. The values shown in the RGB parade are the intensities in the red, green and blue channels of the video signal. When red is at 100% and other components are at 0%, the result will be saturated red. When red is at 100%, green at 100%, and blue at 0% the color will be saturated yellow. When all components read 100% the result will be white. Read up on additive color for more info. Saying that RGB parade isn't useful because it isn't showing luminance is completely discounting that we don't see in black and white.

                     

                    Each scope is just a different view of the colors and is more or less useful depending on the characteristics of the footage and how you grade. There is a certain amount of overlap that allow the same task to sometimes be done with multiple scopes, but each offers something unique as well. As a different view, the RGB parade can show things that wouldn't be obvious with other scopes, for example clipping only in the blues or incorrect color balance between red and green, but only in the shadows. RGB parade is also particularly intuitive for correctors that are described in RGB such as RGB curves.

                    1 person found this helpful
                    • 7. Re: RGB Parade vs YC Waveform
                      Sengstack Level 1

                      Thanks Steve.

                       

                      Two follow-up questions:

                       

                      1) You say the RGB Parade shows intensity. Is there a component in the various representations of RGB -- HSL, HSB or YUV -- that is the same as intensity? If not, how is it calculated?

                       

                      2) You note that the YC Waveform scope display Luma, not Luminance. Which kind of Luma: Y' (Y prime, which has Gamma correction) or Y (without the Prime notation) which is another name for Luminance.

                       

                      The scope name does not use the Prime symbol but I believe it is Y' because the color display matches the standard Y' calculation:

                       

                      Y' = 0.299R + 0.587G + 0.114B

                       

                      This is weighted to represent how humans see color.

                       

                      Jeff


                      • 8. Re: RGB Parade vs YC Waveform
                        SteveHoeg Adobe Employee

                        1) The RGB parade shows the red, green and blue component values. Each of these do not correspond directly to a single component of the other color spaces you mention but are computed as a mixture of them. As you point out for luma, Y' = 0.299R + 0.587G + 0.114B for Rec. 601. Rec. 709 specifies different coefficients. Each of R, G & B can be computed from luma and chroma by taking the inverse of this equation. Y' is a weighte combination of all of R, G & B just as in the other direction R is a weighted combination of Y', Cb & Cr.

                         

                        2) Correct, the YC waveform displays luma, Y', not luminance, Y.

                        • 9. Re: RGB Parade vs YC Waveform
                          Sengstack Level 1

                          Thanks Steve. This is very helpful.

                          Jeff 

                           

                           

                          • 10. Re: RGB Parade vs YC Waveform
                            tfi productions 44 Level 1

                            hello,

                             

                            i just found this link to what looks like a cool program to do what you guys are talking about:

                             

                            synthetic aperture testgear 2.5

                             

                            check it out

                             

                            it has a bunch of scopes

                             

                            any move advice is appreciated...

                             

                            may be overkill or just the right touch to a broadcast workflow...

                             

                             

                            j

                            • 11. Re: RGB Parade vs YC Waveform
                              lasvideo Level 4

                              Ive used  Test Gear for several years now. It allows you to have scopes to reference while in AE. I would still continues to use the scopes available in PrP when I was working in that application. But when I dynamic link to AE Test Gear provides me the ability to have scopes in AE as well.