Colour conversion value in Dialog

[huub]

I was wondering what the value means in de Video Colour conversion option. I suppose its the colour space found in the content!! Adding rec 709 content it shows Rec 709 assuming it will convert from REC 709 to XYZ. I did in Adobe Premiere a TIFF export (16 bit) from Rec 709 footage and found that its always creating RGB files. ( tag 0x106 = 2) . Adding this content to DCP-o-Matic the Colour Conversion value still shows me Rec 709.
What would be the correct Colour Conversion value ? .

[Carsten]

It should be sRGB. Which is very similar to rec.709.

When I add a 16Bit TIFF (or other still images), DCP-o-matic automatically chooses sRGB. In general, the automatic color conversion applies sRGB to single images, and rec.709 to typical HD video formats.

However, for a numbered image sequence, DCP-o-matic chooses rec.709, probably considering that they will come out of a video processing pipeline.
It depends a bit on what Premiere actually does when exporting to TIFF sequences. As they are marked as sRGB, I would assume they are indeed conformed to sRGB color space.

The difference can usually only be seen in shadow areas of the image, there is a slightly different gamma curve applied in dark areas.

You can always override if your are not satisfied with the automatic choice.

- Carsten

[huub]

thanks for the fast answer Carsten. I needed a week to study and dig deeper in Color profiles.

I guess the fact is that with DCP-o-Matic you have to know what color spaces are used in the content added. It does not detect e.g. embedded color profiles (unless you add a DCP )

I'm not a film or color person , I am an IT-guy trying to understand something new to me. I tried to create a TIFF sequence in JPEG2000 compression and the XYZ color space so the DCP creation would be fast. The REC 709 in the dialog confused me.

[Carsten]

It is not a good idea to bypass DCP-o-matic JPEG compression - because, there is no 'one size fits all' JPEG2000. DCPs need to follow a strict set of rules, a so called DCI profile, in order not to crash the server at playout. Other, more general JPEG2000 encoders mostly do not apply or even know these special constraints. We have seen issues with external J2K encoders often. The trouble is, people then blame DCP-o-matic, because they created the DCP with it. But if you add a J2K file created by an external tool, the idea is that DCP-o-matic should not touch it, but simply pass it through.

Many people think that creating 16 Bit TIFFs,DPX or similiar master files guarantees the best quality. The trouble is, there are many ambiguities in video transported that way.

- Carsten