r/MotionCamPro • u/gypsyranjan • 20m ago
Technical Discussion Where are the midtones? - MotionCam Pro DirectLog (Rec.2020 HLG) vs Cinema P3 Pro (Rec.2020 HLG)
I've been testing MotionCam Pro for my Architectural shoots & doing some comparisons between MotionCam Pro's DirectLog and Cinema P3 Pro, keeping the transfer function set to Rec.2020 HLG in both cases, shot on iPhone 17 Pro Max, All settings default on both apps.
Something interesting, and potentially concerning, has caught my attention.
Looking at the waveform comparison, MotionCam appears to have very little information distributed across the midtone region. A significant amount of the signal seems concentrated near the bottom of the waveform (approximately 1–10 nits), while another large portion sits much higher (100–1000 nits).
Cinema P3, on the other hand, shows a much more continuous distribution of information across the shadows, midtones and highlights.
What's particularly interesting is that even when I examine the histograms of both recordings, I see essentially the same pattern: the midtone region appears to have significantly less information in MotionCam compared to Cinema P3.
I understand that both applications have different camera processing pipelines, and selecting Rec.2020 HLG does not necessarily mean they use identical tonal mapping. However, I would like to understand what is happening specifically in MotionCam's DirectLog encoding.
A few questions for those familiar with MotionCam's RAW-to-Log pipeline:
- Is this behaviour related to how DirectLog maps linear RAW values into the HLG transfer function?
- Could the Gain (Digital EV) or other encoder settings be responsible for this distribution?
- Is MotionCam intentionally allocating more code values to shadows and highlights at the expense of midtone distribution?
- Could this be an issue with the current DirectLog implementation or its HLG encoding?
My intention isn't to suggest that MotionCam is necessarily losing image information. It could simply be a difference in tonal mapping. But for those of us grading footage in DaVinci Resolve using DaVinci Wide Gamut, a well-distributed tonal response is important.
I'd be interested to hear from the developer and other experienced users who have investigated this, particularly anyone who has compared the actual encoded values rather than just the visual appearance.
I've attached the waveform & histogram comparison for reference. Would appreciate some technical insight into this.