David Katzmaier/CNET

The number of big-name 4K video services just doubled, from one to two.

Amazon announced the inception of its 4K streaming service today, joining Netflix in allowing owners of many 2014 4K TVs to watch a selection of 4K/Ultra High Definition movies and TV shows.

Prime members as usual get the best selection, gaining access to numerous 4K shows without having to pay an extra dime. Amazon Original Series like "Alpha House," "Transparent" and children's series "Gortimer Gibbon's Life on Normal Street," as well as the BBC series "Orphan Black" are said to be available now.

A few Sony Pictures films are also available in 4K streaming free to Prime members, including "Crouching Tiger, Hidden Dragon," "Funny Girl," "Hitch" and "Philadelphia."

Non-Prime members '4K choices are more limited. They get the concert "Tony Bennett & Lady Gaga: Cheek to Cheek Live!" in Ultra HD for free (sponsored by LG), as well as the ability to purchase a selection of Sony Pictures movies in 4K starting at $19.99. Titles available at launch include "American Hustle," "Captain Phillips," "The Monuments Men," "This Is the End" and more.

To watch Amazon's 4K stream, you'll need a compatible 4K TV from 2014; Samsung, LG, Sony and Vizio have all announced that their sets will handle the updated app. As with Netflix, Amazon's 4K stream utilizes HEVC/H.265, so most 4K TVs from 2013 are not compatible. Sony's FMP-X10 player will get Amazon 4K streaming in spring 2015.

David Katzmaier/CNET

Hands-on: Better streaming, but not better than Blu-ray

(Updated 12/10/2014) After initially failing to find the 4K/UHD section of the updated app yesterday, I contacted Amazon whose rep directed me to look for a specific "Ultra HD" tile (above).

This morning I rechecked a few of the 4K TVs I had on-hand in the lab -- a Samsung UN60HU8550, Sony XBR-X950B , LG 65UB9500 and two sizes of the Vizio P series -- and the LG and Sony showed the tile. The Vizios did not, so I wasn't able to test Amazon's 4K stream on those sets. (Update 12/12) As for the Samsung, it showed the tile and streamed Amazon 4K only after I updated the Amazon app itself in addition to the TV's main software.

Using the Sony as my main 4K source, I compared "Ultra HD" (aka 4K) streaming on Amazon to "1080p HD," the highest quality available to non-4K sets. In side-by-side comparisons of "Alpha House" and "Crouching Tiger, Hidden Dragon," the 4K stream did look better than the 1080p versions, with improved detail and sharpness in most areas, in particular faces and fabric textures. The difference was visible from my nominal seating distance of about 8 feet from a 65-inch TV -- sitting closer will make the difference more apparent, while moving back it will dwindle.

The differences seemed more obvious than what I've seen comparing Netflix's 4K streams to its highest non-4k quality, called Super HD (1080p), for example in the Samsung UNHU9000 review. I suspect that's because Netflix's Super HD looks better in general than Amazon's "1080p HD," but without more testing I can't say for sure.

I was also curious how Amazon's 4K stream compared to an actual Blu-ray, so I paid $19.99 for "The Amazing Spider-Man" on Amazon and tracked down my Blu-ray copy of the film ("Mastered in 4K" but as with all Blu-rays, "only" 1080p resolution) to find out. I wasn't surprised that the 1080p Blu-ray outperformed the 4K video stream, but I was impressed by how close the two were. I had to look close to spot the Blu-ray's sharper, better-defined details in the face of Gwen and Peter's parents, for example, and the textures of their clothing and hair. The 4K stream looked exceedingly good, as good as any streaming video I've seen.

On the other hand, when I showed the side-by-side TVs to a colleague, Ty Pendlebury, he picked out the TV showing the 4K stream as the best, citing what he saw as better detail.

The stream remained consistent at the highest levels, a testament to the excellent broadband at CNET's lab. I had to queue up four TVs' streams simultaneously before one failed with Amazon's "the video is taking longer than normal to load."

This quick test was imperfect -- there were plenty of variables including different TVs and calibrations -- and I plan to put a variety of 4K sources to the test vs. Blu-ray early next year. But in the meantime, it indicates that 4K streams and Blu-ray are very close in quality, and I'd wager most viewers would have a difficult time telling them apart.