8 Replies Latest reply on Aug 4, 2008 9:52 AM by rasworth

    DNG Profile Editor internal operation question

    rasworth Level 1
      Eric/Thomas,

      I have a reasonable understanding of colorimetry and appearance modeling, and am familiar with ICC profile construction and usage. However, I'm having difficulty understanding what the quantitative results are when using DNG PE. I have read thru the latest DNG Specification, with lots of attention to Chapter 6.

      It appears that recipe table entries affect only the ProfileHueSatMapDataN LUT's when applied to a profile (ignoring wizard usage). Is a table entry CA'd up and down to the 6500 and 2850 LUT's, or transferred absolutely to each? I suspect the latter, in which case the table modification is only "accurate" if the same illuminant is used as for the reference image.

      Thanks for your help,

      Richard Southworth
        • 1. Re: DNG Profile Editor internal operation question
          MadManChan2000 Adobe Employee
          Yes, the recipes are used to tweak these LUTs. If you specify separate adjustments for the 2 tables (A and D65) then the actual LUT that will be applied to a given image will be a linear combination of these two LUTs, where the weighting factor is derived from the image's white balance (which in turn describes the color temperature of the illuminant).
          • 2. Re: DNG Profile Editor internal operation question
            rasworth Level 1
            Ok, but my question is a little different. The default operation of the DNG PE for recipes is a given table adjustment will be applied to both LUT's (BTW I believe that should be changed, or at least flagged) when the receipe is used to generate a profile. If I bring in a reference image at a white balance of 5000 or so and use it to derive a table color, will the color be chromatically adapted to each LUT for entry?

            Richard Southworth
            • 3. Re: DNG Profile Editor internal operation question
              MadManChan2000 Adobe Employee
              There is no adaptation, because all LUT adjustments are deltas, not absolute numbers. That is, each element in the table is a shift (hue shift in degrees, saturation and lightness scale factors).
              • 4. Re: DNG Profile Editor internal operation question
                rasworth Level 1
                Yes, but as I read the DNG spec the LUT's are HSV in and HSV out; therefore the "before" color (after conversion to HSV) drives the 3 dimensional table and the "after" color is the output (or outputs after smoothing for neighboring values). My question is whether or not the "before" color is CA'd before it drives the table index's.

                Richard Southworth
                • 5. Re: DNG Profile Editor internal operation question
                  MadManChan2000 Adobe Employee
                  All colors in the DNG processing model are D50 the moment the initial matrix is applied. With the new profiles, specifically, white balance is performed by scaling the camera coordinates as needed, then a 'forward matrix' is applied that maps camera white (1,1,1) to D50 white. From that moment on, including all/any LUTs applied, all colors are with respect to a D50 reference illuminant.
                  • 6. Re: DNG Profile Editor internal operation question
                    rasworth Level 1
                    If I understand correctly, creating a recipe with "Edit Both Color Tables Simultaneously" checked and applying it to a profile will result in both HSV LUT's being modified identically, i.e. same HSV coordinates indexing the LUT's and same HSV output values.

                    It appears to me that it makes no sense to modify one of your new profiles, with separate 6500 and 2850 sections, with a recipe set to "Edit both Color Tables Simultaneously" turned on. The only time it would make sense is when modifying a custom profile created with the wizard for a single illuminant. This is a confusing area in the use of the PE and I believe you need to modify the UI, per my other post.

                    Richard Southworth
                    • 7. Re: DNG Profile Editor internal operation question
                      MadManChan2000 Adobe Employee
                      We expect the common use case will actually be Tutorials 1 and 3, which means opening a problem image, using the PE to fix the colors as desired, and exporting the changes. That's why Edit Both Color Tables Simultaneously is the default choice. Otherwise the user would have to know what the color temperature of the image is before deciding which table to edit, which gets confusing.
                      • 8. Re: DNG Profile Editor internal operation question
                        rasworth Level 1
                        Eric,

                        I have no problem with Edit Both Color Tables Simultaneously being the default choice; my objection is not seeing it's selected. I believe it should be a third choice in the Color Table box instead of an option. IMO it's more confusing for the Color Table box to indicate "6500" leading the user to believe it's the only selected table, not knowing that because the option is checked both tables are being modified.

                        Richard Southworth