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Experiment:Grading in Resolve Lite on an sRGB computer monitor- emulating rec709
  • The goal of this exercise is to be able to grade footage in the preview window on a PC in Resolve Lite that when output to a rendered video file (direct file playback via a PS3, DVD or AHCD format disk) and played back on an HDTV will be as close as possible to what the preview in Resolve Lite is displaying. I know this is not broadcast standard in any sense, it's not 10 bit so blacks will not have the detail as it cannot be perceived in an 8 bit color space that this inherently implies, but it will look as closely as intended in the grading process given the absolute poor working conditions I'm imposing.

    As I came to discover Resolve does not use any color management in it's preview window when editing. Tricks like limiting the output levels in the control panel of the video card driver do not have any impact on the output of the preview window. As well I don't have space or money to connect a second output interface with a separate TV to my system for proper monitoring when color correcting, let alone a broadcast reference monitor!

    First I downloaded the rec 709 calibration video clips from AVS forum ( calibration) in mp4 format.

    I also set up in my video card driver settings to limit the output when playing back video in video players to 16-235 levels. This would allow quick verification on the PC of the results I was getting when playing back the files created in Resolve Lite.

    I created a new project in Resolve Lite and in the settings for the project, I created 1D soft clip LUT with no reference LUT to begin with using an upper clipping limit of 880 instead of the default 940- this was trying to get as close to the calibration video clips defined upper white point- and loaded this as the 1D display LUT - but not in the output LUT! I only wanted to SEE the effects of limited output and to not bake this into the final output file.

    I loaded in the calibration clips into the project. In a track node I added a point in the center of the RGB curves, ganged, and offset it ever so slightly negative to try and counter-act the gamma 2.2 of my PC display to emulate gamma 2.4 of the rec 709 spec. I then took a grab of this and saved it to a project with only this node as any CC.

    The idea here was to create an output limiter with the soft clip LUT to get as close to rec 709 levels and gamma as possible with the naked eye, based on clips that are used to calibrate HDTVs in the rec 709 color space.

    To see how this would work out, I loaded a separate project that had some CC on multiple clips. In the project settings I loaded the soft clip LUT as the 1D display LUT. Afterwards, I added two serial nodes to the track node (not the clip nodes- tons of individual adjustments per node). In the last node for the track I loaded the node from the grab taken in the previous project in the gallery to apply a simulation of rec 709 display levels.

    This gave a rather washed-out final output to the clip as to be expected! I used the first node in the track nodes to adjust the lift/gamma/gain and tweaked saturation levels and shadows and highlights a bit in the log color wheels to get a final look that had the contrast and brightness I wanted.

    In the deliver tab rendered out to Quicktime H.264 so that I could rewrap to mp4, video safe colors (NOT FULL RANGE).

    Re-wrapped the MOV files to mp4 using mpeg streamclip.

    Opened up the output from the grade in windows media player on the PC (which is having its levels moderated by the video card driver) and the look was very close to that as what I was previewing in the Resolve Lite preview window. Loaded this on my PS3 which has been set to output limited (rec 709) colors to an LG 37" IPS panel HDTV.

    Calibrated the TV using the same reference clips as used to start creating the emulation curves in the first Resolve project, matching as close as I could by memory to the tweaks done in terms of the white clipping point specifically.

    Results so far are very good- the range of mid-tones and shadows are perceptually very close to what I was going for in the Resolve preview window on the PC. I've found this method to give me close results at final viewing on the HDTV from the grades performed in Resolve Lite. Previous attempts without trying to emulate the rec 709 space were all over the board, trying to compensate with what I thought would deal with the different levels between full range output at gamma 2.2 when grading in Resolve Lite on the PC and the limited rec 709 levels output at gamma 2.4 displayed by the HDTV. That's just crazy impossible to try and do! However I don't have the TV and the editing PC in the same room or the same viewing conditions, so I'm sure I'm not 100% matched by any means because I can't view the results side by side.

    I know this doesn't give near the quality results as working with a reference monitor would. However it allows some level of consistency in the grading process on the PC, getting a final look on an HDTV that is more-or-less what I see when grading using the preview in the GUI of Resolve Lite.

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  • Just to say any critical feedback or other experiences trying to do something like this is fine by me- I want to be able to correct my perceptions of what I'm doing if anybody else has anything to correct/add/inform!