HDTV Resolution and Pixel Count?
Q. Regarding Alan Lofft's column entitled “Standard or High Definition: It's All in the Pixel Count,” if I have a Samsung DLP HDTV that has a native resolution of 1280 x 720p and I'm watching HDNet, which uses a 1080i signal, there is no way I'm going to get the number of pixels that come with that 1920 x 1080i format . . . right? The native resolution on a set is the maximum number of pixels that can possibly be displayed? Also, do the 720p and 1080i figures refer to the horizontal or vertical number lines? Thanks for answering my questions on pixel count. - Patrick
A. The 720p and 1080i figures refer to the number of horizontal lines stacked vertically from top to bottom of the screen. Those are also called “vertical resolution.” The 1280 and 1920 figures (called “horizontal resolution”) are the total number of individual pixels (picture elements) across each of the horizontal lines for the 720p and 1080i formats, respectively. So it's true that in your example you won't get all 1920 pixels of HDNet's horizontal resolution from your Samsung's 1280 x 720p display. The Samsung DLP, a plasma, or an LCD panel are all "fixed-pixel arrays,” and the Samsung's micro-mirror DLP chip has a native resolution of 1280 x 720p. Likewise, a plasma or LCD flat-panel will have a fixed number of pixels across each of its horizontal lines which may or may not exactly correspond with the transmission standard, just as the 1920 pixels that HDNet uses aren't an exact fit for the 1280 pixels of the Samsung DLP chip. But that doesn't matter because the Samsung or plasma set's internal digital scaler will automatically convert all incoming video to “fit” its native resolution. And in my experience the differences, if at all visible, are very tiny. The really visible differences occur at a pixel count between 480p and 720p, or between 480i and 1080i, the differences between Standard Definition and High Definition.
Moreover, the overall clarity of a DVD displayed on an HD set is affected by the original movie or program's aspect ratio, which may not be identical to the 16:9 (1:85:1) widescreen standard adopted for HD. If you watch some extremely widescreen movies such as “Lawrence of Arabia” (2:35:1), not all the pixels are used by the scanner during the digital transfer to DVD. Consequently, when you watch playback on your HD widescreen set, there will be black bars at the top and bottom of the image, even on a 16 x 9 display. This lessens overall resolution, because all the pixels used to display the black bars are not used for image display. Fewer pixels used for picture content equals lessened resolution. It's visible, but in my opinion this variation in pixel count is not a big deal.
About the Author
Alan Lofft was, for 13 years, Editor in Chief of Sound & Vision, Canada's largest and most respected audio/video magazine. He edited Sound & Vision (Canada) until 1996, when he moved from Toronto to New York to become Senior Editor at Audio magazine.
Lofft has been writing about hi-fi and video professionally for over 20 years, ever since his first syndicated newspaper column, "Sound Advice", began appearing weekly in The Toronto Star, Canada's largest-circulation daily newspaper. In the late 1970s, he became a contributing editor, columnist, and equipment reviewer at AudioScene Canada, the leading national consumer electronics magazine at the time.
He also wrote on consumer electronics for Maclean's magazine and made occasional appearances on TV on "Canada AM," the national CTV morning show, and on June Callwood's national afternoon TV talk show.
In 1983, he was appointed editor of Sound Canada magazine, which he relaunched in 1985 as Sound & Vision, incorporating video content and reviews as well as hi-fi and audio features. He also became a contributing editor to Stereo Review in New York, and an audio columnist for Music Express, a Canadian rock magazine.
An audio and electronics enthusiast from childhood, Alan began building vacuum-tube hi-fi gear for his father, who was an audiophile in the 1950s. Lofft's passion for audio continued through college, during which time he hosted and produced "On Campus", a radio show taped on location (on a portable Ampex 650 open-reel recorder) at Wilfrid Laurier University and broadcast locally in Kitchener, Ontario.