Screen quality and cost mostly! Just about all the HD Ready sets have a lower screen resolution, at about 720p. Whereas Full HD sets are all above 1080p.
HD Ready – also known as 720p
This is the entry level in High Definition television sets. These will all work with your HD devices or broadcaster signal, but it will downgrade the signal to the 720p resolution, if transmitted at 1080.
Full HD – also known as 1080p
These type of HD sets, will be able to display full signal without having to downgrade the signal. Although these are the perfect purchase, they come at quite a price, and often is difficult to tell the better resolution. Remember that the device being read, like a DVD or a signal from DSTV, will have to support the 1080p resolution to see the true value in these sets.
Good news! On smaller television sets (48″ or less) you will not really notice the difference. If you are connecting a computer to the screen, or you plan to sit as close to the TV as it is big, then you should go for the Full HD with a screen smaller than 48″. Otherwise save your money.
Not so simply:
Although digital is now way better than analogue, you still have two types of screen refreshes, Interlaced and Progressive.
Interlaced scanning (i)
All the analogue screens operated with this type of scan. Simply put, it displays the image on the screen in alternative screen scans, first lines 1, 3, 5, 7 etc (field1), then follows with lines 2, 4, 6, 8 etc (field 2). This happens rather quickly, close to 30 frames per second per field. The flicker we notice in a TV set is as a result of this type of scanning.
Progressive scanning (p)
The new HDTV sets use progressive scans. The image is displayed one line after the other, and does not skip lines to return and display the rest. This also happens rather quickly at 60 frames per second. This produces less flicker from the screen.
720p – 1280×720 progressive scan
720i – 1280×720 interlaced
1080p – 1920×1080 progressive scan
1080i – 1920×1080 interlaced
Thanks to AnchorBay for the images: www.anchorbaytech.com