Ultra HD TV has more than four times pixel count in the same size screen than a normal HD TV. A 4K UHDTV is 3840 pixels wide by 2160 pixels high to make the total pixel count as 8.3 megapixels. This is four times the pixels count on a normal HD TV of 1920x1080 pixels which totals to 2.1 megapixels. Hence obviously we would expect the picture quality of the Ultra HDTV to be much better than a normal HD TV.
If you are seeing the ultra HD TV picture close-up, then the picture quality is far superior to a normal HDTV also watched close up. But if you were to view both an Ultra HD TV and a normal HD TV side by side at normal viewing distance of about 10 feet, then the difference in the picture quality between an Ultra HDTV and normal HD TV will look the same. Main advantage of Ultra HD TV is when it is viewed close up.
The main differences between ordinary HDTV and an Ultra HDTV are as follows :
An Ultra HD TV has more than four times resolution compared to a normal HDTV. Resolution is the number of pixels arranged horizontally and vertically across the screen. Pixels, as explained in our 'TV Specs' page, are the smallest part which makes up the whole picture on the TV screen. The higher this pixel count per unit area means picture density is higher with better the picture quality. The pixel per unit area or the picture density is referred to as 'PPI' or pixels per inch. Ultra HD TV has four times the PPI compared to a normal HD TV.
HDTV picture has a total of 1920 pixels across the screen horizontally and 1080 pixels on the screen vertically and is written as 1920x1080 and this results in a HDTV picture of 2 million plus pixels or 2 Mega Pixels. Ultra HDTV often called 4k ultra HDTV or ultra 4k HDTV has typical resolutions of 3840 X 2160 pixels or even higher. A resolution of 3840x2160 in Ultra HDTV yields a picture of over 8 million pixels or 8 Mega Pixels, which is four times the resolution of Full HDTV. The Advantage of having such high resolution in an ultra HDTV is that the picture can be viewed from close distances and it will be less pixilated, that is not having a grainy appearance. Ultra 4k HDTV pictures are like high quality print pictures on a TV.
The Contrast Ratio of 4k ultra HDTV will be about the same as the base HDTV type depending on the base technology used. For example if it is an LED 4k ultra HDTV, it will have the same contrast ratio of similar LED HDTV and in the same way, if it is an OLED 4k ultra HDTV, it will have the same characteristics of contrast ratio of an OLED HDTV. The higher cost 4k ultra HDTV however improve on the contrast ratio by having better local dimming backlights for LED 4k ultra HDTVs.
The refresh rate of 4k ultra HDTV will be the same as the base HDTV and which depends on the base technology used. For example if it is an LED 4k ultra HDTV, it will have the same refresh rate qualities of similar LED HDTV and in the same way, if it is an OLED 4k ultra HDTV, it will have the same characteristics of refresh rate, contrast ratio, etc. of an OLED HDTV.
4k ultra HDTV will have to transfer much more data through its TV connectors and cables. For this higher quality connections, especially the HDMI connectors for 4k ultra HDTV has to be of a higher quality. Now the standard HDMI 1.4 connectors can handle only upto 30 Hz that is 30 frames per second. To get higher frame rates HDMI 2.0 which has been already announced will be required.
One of the major drawbacks of 4k ultra HDTV is the availability of 4K Ultra HD TV content. The ultra 4k HD TVs in the market now are capable of up-scaling standard HDTV pictures to play on their ultra 4k TVs, but real 4k ultra HDTV content is hardly available. Soon Blu-ray disks will be available with 4k ultra HDTV movies, but regular 4K ultra HDTV transmissions over broadcasts or by cable or streaming 4k movies over the internet by Netflix is a long way off.