Hi. I have a bunch of files I need to do some tests with. They were shot on an iPhone I think, they are all Dolby HDR. I just need the files looking normal in boring old REC709. I can’t seem to do it through the colour Management node. I’ve tried View Transforms from REC2100 HLG to ACES, then ACES to REC709, but not really working.
The files are also HEVC/H.265, so I have had to transcode them to read them in Flame. I did the transcodes via an upscale in topaz. At the other end of that process I get ProRes files in REC2100 HLG, but I can’t get them in to REC709 and looking normal without doing some weird dodgy colour grading myself.
Just wondering if there’s a more elegant solution?
First I would recommend investigating Apple’s Compressor for your transcode. Lots of things could be going on inside Topaz and eliminating that variable might help. Compressor is built for this sort of thing, will probably be using the latest and greatest iPhone color math, and will give you options for input and output colorspace.
Second, depending on what you get back from that, you might play around with the rules in View Transform. I have, in the past with “other devices,” had luck with things like Aces1.1 SDR with P3 primaries (or whatever it’s called), instead of relying on Flame’s default VT rules.
Third, iPhone HDR can be quite hot, in my experience, and squishing it down to 709 is probably going to be pretty lossy. I would not be surprised to learn that there is no trauma-free path between those two formats.
I did this the other day with pretty decent luck. I’m not sure if it was the “right” way, but it got it to Rec709, in flame, looking like it did on the desktop on a mac with a little bit of room to fiddle with it. I put it through Media Encoder set to quicktime, using the preset ProRez4444 HQ HLG. This set the colour space to Rec.2100HLG. It also sized it up to 1920. I had to manually set the size to remain native. I imported the result into flame with a view transform. The source was tagged as Rec2100 HLG (Lw=400nits, gamma=1.2) The view transform was Rec 709 OOTF and display was Rec709 video.
Correct? I don’t know, but it got me on my way.
I’d try an input transform in Flame, take the Rec2100 HLG then transform it to Rec2100PQ then use the Dolby Vision tools to derive your SDR from that. Works better on graded pictures but you should get a decent result to work with.
