Saturday, August 10, 2013

4k TV...

Debbie and I were down the hill yesterday, doing various and sundry errands.  Along the way we had a lovely meal of eastern scallops, definitely the best part of the day!  We also ran into completely unreasonable traffic, reminding us once again of why we really don't like coming down off the hill very much :(

But one of the things we did was kind of fun – we wandered into Fry's Electronics to see what a 4k TV (also called Ultra High Definition TV, or UHD TV) actually looked like.  The model we looked at was one of Sony's latest.  They're quite expensive now, but certain to come down in price very quickly as more manufacturers get into the game and the competition heats up.

We weren't there to buy one, just to look and see what the fuss was about.  We own an HD TV now, so that was the benchmark for our comparison.  Both of us were very impressed; in my case, much more so than I was expecting to be.  What got my attention was this: from four feet away from the screen, if I stood perfectly still while watching an outdoor scene, I could almost imagine that I was looking at a window and not a TV.  The result was better than any slide projector I've ever seen – so immediately I thought about what a great way to show off still photography this would make.  The movies were impressive, too, but I rarely watch either TV or movies, so that's not too compelling for me.  Debbie, on the other hand, is a big movie fan, and watches quite a bit of TV, too.  Her reaction was to comment on the three dimensionality of the sample movies, and the resolution.  When content is available (and the price comes down!), she wants one.

Reader and friend Cliff F. passed along this article explaining about 4k TV; lots of good information in it.

From a technical guys perspective, there's a lot of marketing spin at work here.  First of all, the horizontal resolution isn't actually 4k (4,096), it's 3,840, yielding an image size of 3,840 x 2,160 pixels (for a 16:9 aspect ratio).  But even this is misleading, as (most of) the cameras used to capture this content don't actually have 3,840 RGB-sensing pixels on a line (which would require 3,840 x 3 = 11,520 sensor cells per line).  Instead, they use sensors with 3,840 sensor cells and a technology called “Bayer filters” that provides 1/4 the areal resolution you think you're getting – then uses a “de-mosaicing” algorithm to computationally estimate what an actual RGB sensor would have seen.  This is, of course, very different than the 3x CMOS cameras, which are apparently impractical for 4k TV; these actually deliver the resolution specified.

Being an engineer, this kind of misleading specification really ticks me off.  If someone told me I was buying a “4k” TV camera with a 16:9 aspect ratio, I'd expect to have a 4,096 x 2,304 pixel TV.  That would imply (to me!) a sensor with 4,096 x 2,304 x 3 (for RGB) = 28,311,552 individual sensors on it.  What I actually get is 3,840 x 2,160 = 8,294,400 individual sensors.  That's less than 30% of what I expected from the marketing claim.  Annoying!

I don't know if the displays for UHD TV are specified in the same misleading way, but I'd bet they are.

In any case, that's all an engineer's rant.  From a user's perspective, the 4k TVs are beautiful, but expensive.  But then, there are a lot of things like that :)

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