Editor's note: Consider this article (now around 6 years old, to be useful to a point. As I add this note, HDMI 2.0 is being launched. That will merit it's own article.
HDMI 1.3a, is the latest (5/08) shipping incarnation of the HDMI standard. One of the features it supports, that previous versions of HDMI have not, is something called Deep Color.
Previous versions of HDMI have been limited to the classic 8 bits per channel (channels being Red, Green, and Blue), for a total of 16.7 million colors. That has been a standard for a great many years, in both digital and analog. However, over those years, there has been plenty of higher bit rate processing going on. You routinely read that this projector or that does 10 bit processing (per channel).
The point here, is that as big as 16.7 million colors sound, it is still a relatively small portion of what the human eye can distinguish. 30 bit color, instead offers approximately 1 billion colors, and HDMI 1.3's Deep color also supports 12 bit and 16 bit. FYI: Photoshop has been able to process 16 bit (per channel color for years.
With standard 8 bit per channel (24 bit), there are only, for example 256 shades of gray, 256 shades of pure red, etc. The human eye, can easily discriminate far more than that number of shades of gray or any particular color.
If you were to look at a graphic, going from white to black in grayscale, with only 256 shades of gray, you would be able to detect each shade from the ones adjacent to it (we refer to that as banding). Move to 30 bit color - and you now have 1024 shades of gray, and it becomes almost impossible to see individual shades, use even greater bit depths (12 bit, 16 bit), and the issue of banding fades away.
So, to start with HDMI 1.3's Deep Color offers several ways to solve the banding issue, and provide smoother more accurate colors, and a wider overall color gamut (the current 8/24 bit gamut, only offers a small portion of individual colors that the eye can detect).
In addition to the 10, 12, and 16 bit abilities, a new algorithm has been created called xxYCC. Instead of the traditional method of mapping individual colors by their R, G, and B components, xxYCC, allows any color from a much larger palette of colors to be specified, although it allows ony 1.8 times as many individual colors to be specified at one time, since there are thousands of colors unused for every one of the 16.7 million we normally specify.
That may sound strange, but if I fully understand it, it plays out this way.
We don't need to be able to see 1 billion (10 bit/channel), or 69 billion (12bit/channel) , or 2800 trillion (16 bit/channel - 48 bit total). We just need to see the correct colors called for.
Consider - an 1080p HD display device, such as a 60 inch plasma, or a home theater projector, has a resolution of 1920x1080 pixels. Do the math, that's roughly 2 million pixels you are looking at. That means all you need to do is be able to display the right 2 million colors. Mostly you'll need far less different colors than that. What Deep Color provides, and more significantly, xxYCC provides, is the ability to specify EXACTLY which colors are to be used, instead of compromising with the closest similar color, which is what happens today witha standard 16.7 million color palette.
Again, there are only 2 million different colors you can display at once, but, you just might need 1697 different shades of blue, and 8 bit/channel (24 bit - 16.7 million colors) can only offer 256 shades of blue. 36 bit, or xxYCC can provide you with far more than 1697 different shades of blue.
Theoretically, xxYCC actually can do it better than 30 bit, and probably 36 bit, because technically, while 36 bit has far more than 1700 shades of blue, it isn't guaranteed to have the exact 1697 shades called for. xxYCC does.
OK, here's the rub. There is no content that can really use xxYCC or, for that matter, most of the higher Deep Color bit depth.
Probably the first heavy use of the larger color gamut (more colors) will come from video games. Each game starts fresh, so it's easy to convert to a new system, whereas movies are coming from old film that was orginally converted to DVD in an 8 bit format.
In theory, though all movies could be remastered to take advantage of the larger color gamut.
Just, don't hold your breath. Look for various animation, to lead the pack (in my opinion). I imagine there is a new generation of professional digital cameras (camcorders) that movie producers can use which will support the higher bit depths, and color abilities, but most movies are still being shot with film, which means how they are converted over becomes critical to improving color.
Sadly, I've read much on this topic, and really can't get a good feel if we will see a remastered black and white Casablanca, with far more shades of gray, or even newer versions of Close Encounters, or, any other movie, that converts from film, and offers newer superior color handling.
Certainly there is a significant improvement in color handling going from traditional (SD) DVD's to Blu-ray, and that's still without Deep Color at this time.
Getting a projector or other device that supports Deep Color, is mostly future-proofing your system, but it may be several years before there is any significant content to take advantage of it.
Hope that helps - bottom line: HDMI 1.3 with Deep Color (and xxYCC), good to have, but no immediate benefits. It's day, however, will come!
(PS. If you have a home theater projector or other display device that doesn't support HDMI 1.3 and Deep Color - don't fret. By the time you want it/need it, no doubt you will be able to replace your current display for a fraction of its original price.
Also, I'll assume your current display looks great now, we are talking about another small, incremental improvement, certainly not a "night and day" improvement.
Lastly, in terms of home theater projectors, now, in mid 2008 a bit more than half of the 1080p projectors (and less of the 720p ones) support both HDMI 1.3 and Deep Color. Some companies - notably Sony - wanted to make sure that they support the audio improvements that HDMI 1.3 allows (Dolby TrueHD, and DTS-HD), which is definitely more imminent, but were less concerned with Deep Color - more of a future product. As a result, in the case of Sony, their highly regarded VPL-VW40 and VPL-VW60 SXRD (LCoS) projectors support HDMI 1.3, but do not support Deep Color. Wise or foolish? I don't know but I do hear fromr readers who are concerned about buying the Sony's because of the lack of Deep Color.
In terms of projectors (1080p), some of those that support HDMI 1.3 and Deep Color include the Epson Home and Pro Cinema 1080 UB projectors, the JVC DLA-RS1x and DLA-RS2 (the older RS1 is only HDMI 1.2 - thus no Deep Color), also the top of the line Sharp, the Panasonic PT-AE2000U, and Sanyo's PLV-Z2000 and so on... In other words, most of today's affordable 1080p projectors, and I assume, that almost all the newer high end models fromt he likes of Runco, and Sim2, also support Deep Color.
Kapisch? (do you get it?)