Archive for November, 2013

HDMI colour space – a crooked bastard!

Thursday, November 7th, 2013 | Gadgets, Insights, Misc, Tech-savvy | No Comments

One would think that hooking up a device to a TV using a HDMI cable would automagically result in a perfect picture. Digital, 1080p full HD, state of the art, out-of-the-box. That’s not true. I recently encountered shitty display quality problems that originated from a faulty HDMI setup.

First, the problem: sometimes black was more like a gray matter, sometimes dark details simply vanished into sludge. I did hate my telly so much for its shitty display quality that I sold it for a few dimes and got myself a new one. But guess what, the problem persisted…

After more investigation on the matter I came across the fact, that there are different colour ranges in different HDMI standards and one handles the range from e.g. black to white from 0 to 255, the other from 16 to 235. This made me think. In case I had a mismatch of these standards, and let’s say my media player sends a lot of dark gray values that range from 0 to 16 and the receiver simply omits all these information and starts with pure black at 16, it’s natural my dark details got lost. Or, the other way around, my media player starts at 16 with pure black while my telly thinks that 16 already is a dark gray, as it starts with black being 0.

So, sending full range and displaying limited range will result in dark areas that are to light and light areas that are to dark.

Sending limited range and displaying full range will underexpose blacks and overexpose whites.

Here is an example (I simply altered the source and target colour ranges with Gimp):

Nature LimitedFull Nature Original Nature FullLimited

The differences may seem subtle (or YOUR display isn’t properly calibrated), but believe me, I love to crawl in dark dungeons on my PS3 or watch horror flicks that make heavy use of the darker parts of the colour palette. My telly looked like the picture to the right all the time and it drove me to sell it for “bad black levels” (just compare the tree’s trunk in the pictures and you will see the difference). Silly me. A perfect gradient illustrates the problem even more:

Gradient LimitedFull Gradient Original Gradient FullLimited

Now, that I have my systems set up right I enjoy using it so much more than before. So, give setting up your expensive home cinema a try, it doesn’t make sense to spend thousands of bucks on the equip and not setting it up properly.

As far as I understand the problem, as long as you have the sending and the receiving device configured the same you are good to go.

One last thought: I hate all the fancy tech shit becoming more and more “easy” to set up yet the problems that come along constantly increase. I never experienced problems with an old VCR or a Super Nintendo – that’s what I call “plug’n’play” 🙂 To set up a modern home entertainment system you need to really dig into it to do it right. Maybe I should look at it from a Dark Souls perspective. It’s a pain in the arse, but as soon as you’re done it’s very very rewarding.

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