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GH5 to Alexa Conversion

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  • #16
    Hybrid Log-Gamma

    Hybrid Log-Gamma Support Added

    Hybrid Log-Gamma (HLG) conversion variations are now included with each light source, in addition to the V-Log variations. They are indistinguishable from the V-Log variations. Also, the V-Log variations have been updated.
    The documentation PDF will be updated to reflect the new HLG support on Friday.

    Attached is the first in a series of comparisons that will demonstrate the difference between native GH5 color science and Alexa color science. For the conversion image, only the main GHa Daylight conversion has been applied, with no other alteration. The native color image has been matched in contrast and saturation using the Lift-Gamma-Gain controls and saturation slider.


    • #17
      This is pretty good stuff. Thanks mate.


      • #18
        The PDF has been updated to reflect HLG support, as well as an important detail about luminance levels (P3), brought to my attention by Ryan Glover


        GHa Tungsten Main / Native V-Log Color Comparison


        • #19
          Will this work with fz-2500 camera?
          Filmmaker - Author



          • #20
            Originally posted by Joe Giambrone View Post
            Will this work with fz-2500 camera?
            No - that is, its not officially supported. I don't know how different its V-log is from the GH5, but I assume its a different sensor.
            Because V-log L conforms to a very specific, defined standard, GHa may look quite nice with it. But unless its V-log image is identical to the GH5, it won't be an accurate match to the Alexa.
            What I am going to work on next may allow me to support many cameras, but we'll have to see. I won't settle for any standard less than perfect.


            • #21
              Going forward, I will be supporting HLG with [PRE] files, one for Tungsten and one for Daylight. Also, updates to Main and Soft will be going out soon.
              I've been asked for an example of the Alexa conversion on HLG footage. With regards to if it is as good as VLog, it is a precision match.
              I finally got around to shooting a comparison, and here are the stills.


              HLG with GHa Tungsten Main (no further alteration)


              VLog with GHa Tungsten Main (no further alteration)


              • #22
                Something Interesting

                Here are the side by side Log shots (matching exposure & white balance) converted with a popular film conversion software that is supposed to match Kodak 5213.
                These should be identical -

                GH5 V-Log to the software's Kodak 5213:

                Alexa LogC to the software's Kodak 5213:

                Now, GH5 V-Log converted to GHa LogC, and then to the software's Kodak 5213:

                And last, an idea of what the Kodak 5213 conversion is supposed to look like, from the software's website:


                • #23
                  Hi Sage, have you plans making a similar LUT for the new pocket 4k? It has a Sony sensor, it should be similar to GH5s.
                  Would be beautiful having a LUT to match a GH5 and the pocket 4k to the same colors.


                  • #24
                    Absolutely, yes.

                    Ironically, with the Alexa conversion, both cameras will look identical

                    At this very moment, I am working on something incredibly important for the GH5, that will then directly benefit the P4K.


                    • #25
                      Here is are stills from what I'm working on right now, the present-day color science (GHa 'Main')-

                      Last edited by Sage; 09-10-2018, 02:32 PM. Reason: Tungsten


                      • #26
                        Some stills pulled from video of my recent GHa tests.



                        • #27
                          Emotive Color Version 3

                          Core LogC Details

                          - Rewrote engine to work at 65x65x65, main files are now at eight times resolution (supporting files processed at that resolution)
                          - Fine tuned multi-pass/smoothing technique, to achieve absolute smoothness of final files
                          - Introduced Averaging (averaging two separate measurements/conversions of a light source)
                          - Corrected LogC rolloff artifact introduced with Verde
                          - Corrected far magenta-red artifact

                          Emotive Color Component Details

                          - Remade EC component to incorporate new Arri primaries that were quietly revised this summer for Alexa LF release
                          (much deeper, more accurate red placement in relation to blue/green, and subtle hue shifts throughout)
                          - Incorporated 'Sat Lock-Out", like hue lock out, that is fully accurate to saturation distribution between relative hues of Arri RGB primaries
                          (corrects excessive saturation of orange/yellow/green in highlights, and under-saturation of blue in shadows)
                          - Significantly refined saturation model
                          - Unified EC for both WBs (taking a que from Arri's single R709) [Tungsten has significantly more contrast, higher ideal exposure]
                          - Smoother rolloff placement in EC component
                          - Replaced Pop with Linear (no highlight shoulder, better alternative to Arri R709)

                          - Remade all PREs with latest process (at 65, provided at 33) - much more accurate and smooth
                          - Entirely new PDF (and supplemental waveforms)
                          - Added Daylight Skintone SBS
                          - Updated 'Always Already' with V3 (Download 'Original File' - *Avoid watching in Firefox)