Colours coming out different/blacks crushed

[alor]

Hi, I'm new to this, but I can't find anything on it. I open my mp4 video files in DCP o matic and the colours are different. Daylit scenes look very similar if not the same, but dark scenes that get close to black they are very badly crushed. None of the colour conversion settings fix this at all, and I have zero clue why this is happening. What could be the issue and how do I solve it?

I've looked in various export programs but none seem to have options that seem like they could affect this in video export/render settings. Videos are H264 mp4, and are original videos, not rips from movies.

[mytbyte]

You should check whether you exported studio (limited) range or full range video (superwhite, superblack)...it really should be limited range...if you export to, say, TIFF, is it correct?

[alor]

Where do I find these settings?

[mytbyte]

In export settings of your editing or conversion software...actually you may have recorded the video as superwhite (better cameras can do that), and all subsequent steps my be retaining that setting..what camera is it? what software do you use? You could share a few seconds of problem video on PM via wetransfer...

[Carsten]

@alor - what is the source of these videos? Directly off camera, did you feed them through a video editing application?

How did you compare them to what you see in dcp-matic?

- Carsten

[alor]

So far have tested multiple videos with the same issue. One is an older video shot with a GH4, edited and exported from Sony Vegas Movie Studio. The other is a more recent video, shot with an Ursa Mini Pro, edited and exported through Premiere Pro CC earlier this year. Frustratingly, exporting from premiere washes out and reduces contrast in my videos anyway (Vegas didn't) but still not enough to stop these blacks being crushed. I've looked in the export settings for both these programs, plus media encoder and can not find ANY export settings for Studio range, superwhite or superblack. If anyone could point the location of these settings out to me in any of them, that would be very helpful. The UMP may have recorded superwhites and blacks but it was exported without any special settings after a grade. I don't think the GH4 can do that though I'm not sure.

Here is an example of what is happening to my video. https://imgur.com/a/GzNvm

This is an example of a scene which includes light and dark areas. In shots with only dark areas (a few) it's almost pure black and the transition between black and not black is not very smooth. As you can see I have set colour conversion to none here, but I have tried all of them and the differences are very slight if anything at all. The blacks in particular, seem to be completely unaffected by changing colour conversion settings.

[mytbyte]

OK, have you actually built the DCP and play it in a proper player (say EasyDCP demo version - make a 15 second test), the preview in DCP-o-MATIC is always presented more crushed than in the final build, and even DCP playback in Stereoscopic player, from my experience. There may be a slight difference due to multiple gamma conversions, however...And I'm not sure about selecting None for the conversion in DCP-o-MATIC, I find Rec709 to produce the same result as input files if they are graded to standard monitor/TV colorspace

[Carsten]

Well, first of all, I clearly see the difference in your screenshot, and it would worry me as well initially, but you always need to see the DCP on a real DCI projector. People would think that any display rendering can be adjusted for this digitally, but then again, why would we need expensive cinema projectors when a cheap rec.709 display can create the same visual impression?

Using 'None' actually does not immediately display the resulting conversion (which, in my opinion, qualifies as a bug), as 'None' will introduce a massive colour and gamma shift, that you will notice when playing back the DCP created with it. I think, in order to help users to deal with color conversion, the preview should reflect the chosen color conversion by applying it, convert to XYZ and back to sRGB for display, so that you get a decent visual feedback.

Other than that, I don't think that DCP-o-matic is able to render a fully color corrected and calibrated preview any time soon. It is only 'as good as it get's'
It starts with the issue that few user displays are calibrated, or even in a useful/dependable display mode.



- Carsten

[alor]

Oh ok, this is good information guys, because I have exported the DCP in the past and playback of the resulting files still resulted in these issues, but you are saying they will not show up when actually projected? That is good news. Is there a way I can verify this to be certain? One of the videos I am trying to export is a documentary on a country cinema, and said cinema is where I intend to screen these films, but it is a 2 1/2 hour drive from me and I don't have access to any other DCI projectors. Is there any way I can test this to be certain it is correct before I take the long drive down to the cinema?

[Carsten]

Well I guess we can't guarantee wether it will look okay - but it will certainly look really bad when you use 'none'.

You should either let DCP-o-matic choose the color conversion automatically, or set it manually to rec.709 or BT1886.

BTW - since I see VLC in your screenshot - go ahead and create that DCP. You can load the resulting video MXF into VLC, move to an arbitrary position, then perform a video snapshot (not a system snapshot, but a VLC video snapshot). The resulting image is color corrected and should give you some confidence about the blacks.

But without a cinema nearby to verify, it's hard to tell.

When working with DCP-o-matic, I can confirm that the color conversion usually works for me, differences are usually subtle. But if for some reason your footage went through some special range or gamma processing, it may not be converted to expectation.

I would offer to test a short, critical sequence in our cinema, but, would you trust my statement that 'it looks okay to me'?'

- Carsten