Remaking BBC test cards to teach you video processing

https://www.youtube.com/watch?v=U_6HxPkrgcg

by unleaded • 1 month ago

89 6 1 month ago

GL26• 29 days ago

I like the part where they talk about the color perception space. The color perception space has itself multiple representations, according to the distance definition you are taking. The one shown in the video is the CIEXYZ (1931). Since human perception is non linear, there are other definitions which take into account those non linearities to make the space more "Hilbertian", such as CIELAB (https://en.wikipedia.org/wiki/CIELAB_color_space), or CIELUV (1976, https://en.wikipedia.org/wiki/CIELUV). This article sums up well the different representations : https://math.stackexchange.com/questions/1777699/color-space...

zahlman• 28 days ago

When I look at these sorts of diagrams, it seems as if the colours don't blend continuously. Generally I see three rays extending out from the white point that seem much whiter than the surrounding colours, and also a line perpendicular to the "purple" edge which is darker. What's up with that?

rcxdude• 28 days ago

One thing to keep in mind is that the colors on these diagrams are only approximations of what the model is actually representing: even if the colorspace of the image can cover it (which is already unlikely), even very good screens cannot cover it completely. (that said, I'm not sure if that's the cause of the perceptual phenomenon you describe, which I also see on some of them).

helsinkiandrew• 29 days ago

This video has the greatest "Sources and references" section I think I've seen in a YouTube video - 16 videos, over 50 webpage links, and 4 references that don't have links.

jlarcombe• 29 days ago

Very good. Full details of the development of Test Cards J and W here, which I read years ago and thoroughly enjoyed:

https://web.archive.org/web/20100123102758/http:/www.barney-...

Also, Richard Russell's page here:

https://www.bbceng.info/Designs/designs_reminiscences/richar...

who did the technical work.

imagetic• 28 days ago

Dope.

Remaking BBC test cards to teach you video processing

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