RE: Colour communication beyond sRGB

Hi Pierre,

Thanks for your feedback. I have attached a revised version of the spreadsheet that shows my suggested changes. Please let me know if you think I have misunderstood anything - see my comments below.

You said:
> - the table is missing the COLOR.6 (P3 primaries, D65 white point and PQ EOTF)
We can add this. Where does the 'COLOR.6' name come from? Perhaps it would be more consistent (and informative) to refer to this as DCI P3 D65/PQ.


> and COLOR.4 (xvYCC709 as specified in IEC 61966-2-4) systems used in IMF App 2E (SMPTE ST 2067-21)
This is not an RGB space and so can't easily be added to this document. There are a number of such encodings which may be useful to document separately.


> - If I am not mistaken, BT.709 (to display) is specified in BT.1886
> (BT.709 specifies only the OETF)
You are right. However BT.709 references BT.1886 (see note to table on page 3). There are also other references, for example the reference viewing environment is specified in BT.2035 and it could be confusing to include them all. I think it may be better to include only the necessary primary references for each encoding.


> - Shouldn't the "to display" tab should be split into "display colorspaces" and "encoding colorspaces",
> i.e. pixels are not encoded in the DCI P3 D55 colorspace and many displays that accept Rec.2020 signals
> cannot reproduce the full Rec.2020 gamut.
I am not sure that I follow this point. Can you explain further? The intent is to describe how the colour data is communicated - in some cases this is with reference to a display and in other cases it is with reference to a scene. The table shows the relationship between what is communicated and the reference display/scene. As I say, I am not sure I have understood your comment clearly so please clarify.


> In fact, perhaps the "encoding colorspaces" tab should
> further differentiate between mastering/professional colorspaces (COLOR.6 and DCDM) from
> colorspaces in use for distribution.
I agree that it would be a good idea to differentiate these. I have indicated spaces not intended for broadcast by highlighting in blue.


> - the sRGB reference monitor peak is 80 nits
Agreed.


> - 48 nits is only required for the Xenon reference white in 431-2
What should we show as the reference white luminance for the digital cinema spaces? Is there another reference besides 431-2?


> - 'Display P3' has been renamed 'image-p3' in the most recent CSS draft [1]
> [1] https://drafts.csswg.org/css-color/

I understand. I have a request from Apple to refer to the space they use as 'Display P3' but I have added (aka Image-P3) on the assumption that these are the same. It seems from the documentation that they are intended to be.


On the CSS documentation for 'image-p3' I see that this talks about 'image-p3' [DCI-P3], however I think these both use different transfer functions. There is also a typo for the y value of the white chromaticity - it should be '0.3290'.

Best regards,
_Craig

Best,

-- Pierre

On Mon, Feb 27, 2017 at 12:35 AM, Craig Revie <Craig.Revie@ffei.co.uk> wrote:
> I would be interested to receive feedback from members of this group
> on the attached document which provides a summary of a range of colour
> spaces used for broadcast and display of colour information that I
> have put together with help from Lars Borg of Adobe.
>
>
>
> Specifically, are there any important colour spaces that are missing,
> have we made any incorrect assumptions, is there anything that we can
> add that would be helpful.
>
>
>
> Best regards,
>
> Craig Revie,
>
> FFEI Limited
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