15 Replies Latest reply on Oct 7, 2014 9:17 PM by Todd_Kopriva

    Alexa color issues in After Effects

    tavmed

      Hello,  I am working with DPX files in After Effects CS6 (Mountain Lion) that are in the Alexa Log C color space with no intermediate color grading or treatment straight from Technicolor.  My problem is this:  I am trying to color correct the DPX files to match Avid DNxHD color graded reference quicktimes that were genereted from the same DPX files using a LUT and a CDL.  In the past I have never NOT been able to match color perfectly using LEVELS by adjusting the color in each color channel individually while comparing it to the clip I am matching it to.  Not only do I find it impossible to match the DPXs made from Alexa raw footage to a color corrected version of this same clip that is in quicktime DNxHD format but I am finding the red channel in the DPX files behave in ways that are unlike anything I have ever worked with before.  I have done extensive research in regards to this issue to no avail.  Technicolor has supplied a LUT for NUKE and SHAKE that along with a CDL, is supposed to recreate the color grade of the quicktimes.  I have used Colorista free to input the CDL values as well as LUT buddy to incorporate the LUT that I was given with no luck.  Even compensation with levels does not work because the red channel will NOT cooperate.  I also used the LUT utility in After Effects with the same results.  I even contacted the person in charge of such things at Technicolor and they admitted that they gave up on After Effects in regards to providing a solution to color matching Alexa footage that has been converted to Avid DNxHD and baked with a LUT and CDL.  I can't be the first person to have run into this issue and there MUST be a solution out there that doesn't involve switching to Nuke.  Anybody?


        • 1. Re: Alexa color issues in After Effects
          Jonas Hummelstrand Level 2

          We delivered 27.5 minutes of VFX from Alexa ProRes 4444 LogC sources (not ArriRAW) and used "Apply LUT" with a LogC to Rec709 LUT generated from Arri's online LUT generator.

           

          Are you sure that the DPXes are created correctly? Can you upload one DPX with a CC:ed frame plus a LUT so I can test it?

           

          Do you have any frames with a Macbeth chart or similar in it?

           

          If you have Creative Cloud and access to the ArriRAW files; download the ArriRAW plugin for Premiere Pro from Adobe Labs and open the clip yourself and look at the raw data so you can identify where in the chain your problem starts.

          • 2. Re: Alexa color issues in After Effects
            tavmed Level 1

            Hi Jonas,  Thank you for your response.  I have  a couple of files for you that I would be interested in seeing how you fare with.  One DPX frame generated from a ArriRAW file which I have been told no intermediate had been done to and one PNG which is a single frame output from the Avid quicktime that goes with it which I have tried to match the DPX to with no luck.  The PNG file is exactly the same as the quicktime it was taken from.  The frame is of a color chart someone is holding up so it is a good one to try color correction on.  I am  including the PNG here but the DPX is 18.7 MB, do you have a way that I can get it to you?

             

            test-png_from_qt.png

            • 3. Re: Alexa color issues in After Effects
              Jonas Hummelstrand Level 2

              I'm assuming everyone has a Dropbox account by now. It's the best thing since sliced bread...

              • 4. Re: Alexa color issues in After Effects
                tavmed Level 1

                Hi Jonas,

                 

                Thank you, I can't wait to see what you have to say about these files.  I did have drop box, ironically I canceled my drop box account after they had a breach in security and my yahoo account got hacked, not sure if the two were related but trying to get a little insight from Drop box resulted in some very unprofessional and unhelpful results so I canceled my account and deleted drop box off my computer   I do have yousendit though, do you have an address I can send you a yousend it to?  If you are not comfortable with that you can log onto my personal FTP site and I can put the file in there.  Sorry for all the hoops.  Let me know what is best for you.

                 

                Thank you!

                • 5. Re: Alexa color issues in After Effects
                  tavmed Level 1

                  Hi jonas,  just checking in to see if you are still there..

                  • 6. Re: Alexa color issues in After Effects
                    Jonas Hummelstrand Level 2

                    Yes, please put the files somewhere where I can download them without

                    having to create an account.

                    A Dropbox "Public" folder and "Copy public link" would be a great way to

                    accomplish this.

                    • 7. Re: Alexa color issues in After Effects
                      Jonas Hummelstrand Level 2

                      Dropbox was hacked? Are you sure about that? They even have two-stage

                      logins now, I'm really happy with my 100+ GB Dropbox!

                       

                      Did you generate a correct LUT with the Arri Alexa LUT Generator?

                      http://www.arri.com/camera/digital_cameras/tools/lut_generator/lut_generator.html

                      • 8. Re: Alexa color issues in After Effects
                        tavmed Level 1

                        Hi Jonas,

                        Please forgive my latency in this response, things have been crazy.  Thank you again for your help in this, here is the drop box link to the DPX file:

                        https://dl.dropbox.com/u/44859261/test-dpx.dpx

                        I will also tell you what I do know,  Technicolor has been taking the ArriRaw files from the Alexa and using the Color Front OSD to convert them to DPX files.  I was told that the DPX files have a LogC conversion LUT baked into them that was supplied by ARRI.  Along with these DPX files we receive quicktimes of the shots in Avid DNxHD format that have been converted to linar color space.  I am uncertain as to the process (if they are produced by processing the DPX frames or if another process is used to generate them from the same ArriRaw files).  I would love to know the answer to this myself.  I also think that a CDL has been baked into the quicktime that is supplied by the director of photography.  I am still collecting information while trying to get shots done as well.

                        With all that said, my issue is still a mystery to me.  Upon any attempt to use (Levels) in After effects to get the DPX files to match the quicktimes that we were supplied by Technicolor, (like I have done thousands of times in the past with no problem until now and only with files generated from the Alexa) I cannot get the DPX to match, the color information in the DPX files acts as if it has been clipped, making it impossible to reach the range of colors in each of the color channels that are being displayed in the quicktime.  Particularly in the red channel.

                        I have the LUT that Technicolor is supposedly using to generate these quicktimes that along with the CDL which I also have and am using Colorista free to introduce to the clip, is supposed to match the DPX to the quicktime but these do not work either nor does any supplemental adjustments. 

                        Somehow, someone at Technicolor is able to go from an ArriRaw file to a quicktime with a specific colr grade that is unattainable by me using the DPX files that I assume these quicktimes were created from.  Sice color is color, I should be able to do the exact same thing anyone else does to a clip no matter what UNLESS the DPX files I have have been compromised which I am told over and over again are not.  This is where I hope you can shed some light on my delima.  If you can take this DPX file and match it to the PNG I pasted into this thread than you are doing somethng I am not and I hope that is the case. 

                        Thak you again Jonas!

                        Clyde

                        • 9. Re: Alexa color issues in After Effects
                          Jonas Hummelstrand Level 2

                          So many variables there, I don't really know where to start.

                           

                          Your single DPX file doesn't have any evidence of clipped values (not

                          completely possible to rule out, but I can at least see a difference

                          on the white and the light gray square on the chart.

                           

                          Have you used the "Apply LUT" effect to apply the supplied LUT (I'm

                          guessing it's a LogC to Rec709, but who knows?) to the DPX files?

                           

                          Like I said initially:

                          If you have Creative Cloud and access to the ArriRAW files; download

                          the ArriRAW plugin for Premiere Pro from Adobe Labs and open the clip

                          yourself and look at the raw data so you can identify where in the

                          chain your problem starts.

                          • 10. Re: Alexa color issues in After Effects
                            tavmed Level 1

                            Hi Jonas,

                             

                            I did use Apply LUT and plugged in the LUT we were supplied.  I also tried it with LUT buddy which looked the same with no suprises.  I also went to the ARRI website and generated several variants of LUTS, each of them having a different effect of the picture, most of which turned it completely black. 

                             

                            I am curious, were you able to do a color correction on the DPX to match it to the PNG file in this thread?  That is what I am unable to do that supposedly Technicolor has no issue with. 

                            • 11. Re: Alexa color issues in After Effects
                              Jonas Hummelstrand Level 2

                              I didn't have your LUT, so without that it would be very difficult to simulate a grade. It didn't look clipped to me.

                               

                              This should be a very simple process of just applying the provided LUT on the provided DPX and you should be done. If they want you to match their grade and you are unable to get close, that means that either you have been provided DPX files which are not representative of the RAW data or have even transferred with a different LUT.

                               

                              If this is Technicolor that are supplying you with the data, that should mean that they know what they are doing, but that also means that they should e able to explain how you can match your results.

                              • 12. Re: Alexa color issues in After Effects
                                tavmed Level 1

                                The LUT is useless to me as are the CDLs.  After Effects seems incapable of processing the information as it was intedned.  Normally when trying to match a 10 bit DPX to an Avid reference clip's color grade, I don't use a lut anyway, I use levels and adjust each channel individually and have never had a problem getting it to match every time.  I have worked with film and digital, lately the Genisis and Red Epic, none of which have I ever encountered an issue using levels to match a color graded Avid quicktime reference.  I am sure that my limited understanding of the Alexa and it's process of conversion from ArriRAW files to DPXs may be an issue.  I have put as much time as I can afford into learning as much as possible.  I am still waiting to hear back from someone at Alexa who I have talkrd to only once and we actually have a representative from Technicolor here today to help clear up the issue so it's likely a moot point by now.  I would have just liked to know how that DPX responded to any attempt by you to match it to the PNG, just as a litmus test.

                                • 13. Re: Alexa color issues in After Effects
                                  tavmed Level 1

                                  Sadly this issue endures.  No one from Technicolor can offer any solutions or insight.  If anyone wants to take a crack at this I would call you a rock star if you could shed light on anything.

                                  • 14. Re: Alexa color issues in After Effects
                                    pmvictor

                                    Hi tavmed.   I just stumbled across this.  Have you had any luck with this?   I have worked quite a bit with the workflow you describe.     DPXs from an Alexa,  but also having to match Avid based color corrections from a CDL.      Sometimes you use a lut,  but other DITs from set don't use a lut when they color correct,  they just do it all in the CDL file and eyeball it.   So some CDLs work with the Arri lut,  while others do not,  it depends on the project.   

                                     

                                    Using a CDL can be a tedious process unless you have some custom code in place,  as no piece of software (including Nuke) can actually read the files without complaining about how the CCID is formed.   However,  once the slope,  offset, power, and sat numbers get put into place,  they give a spot on match to the Avid quicktime made by the DIT.  

                                    • 15. Re: Alexa color issues in After Effects
                                      Todd_Kopriva Level 8

                                      See this for information on working with color of ARRI Alexa footage in After Effects:

                                       

                                      After Effects and Alexa - Part 1 by ChrisZwar