Photography (Level 8)

Resolution Comparison of HD and SD TV Systems
This image compares the spatial resolution (ability to reproduce fine details) of a high-definition (HDTV) television system (left) with a standard-definition (SDTV) television system (right). The difference is obvious and this is identical to the difference you can observe on an HDTV display by switching from HD input to SD input for a given channel. This demonstration ignores any differences due to interlace (or the alternative called progressive scan). The butterfly is a Blue Morpho Butterfly. They produce their highly saturated and brilliant blue appearance through optical interference (rather than light absorption that happens in most materials). This allows them to be very bright while reflecting nearly a single wavelength of light (actually a small range of wavelengths).

Why is Digital TV Better than Analog TV? Is HDTV Really Better than SDTV?

Let's begin with the second question. The image quality of HDTV is clearly superior to that of SDTV. It should also be noted that either level of definition is possible in either analog or digital television systems. However in the USA, HDTV is strictly a digital system. The previous SDTV system was analog and is now obsolete. Currently SDTV signals are also digital. Whether or not HDTV is really better than SDTV is ultimately a personal opinion. If your TV displays shows little difference in your viewing environment, then it is difficult to say that HDTV is better. Also, the content is the same. There is nothing about HDTV that makes the content superior!

The first question can also be a matter of personal preference. In the USA, there no longer is an analog TV system, so the question is moot. It is still of technical interest to compare the systems. Digital TV transmission does not suffer from the artifacts and degradations that were often seen with analog transmission. With digital systems you generally either have a signal or you do not. In analog systems we had artifacts from interlace, from chromatic aliasing due to crosstalk between luminance and color dimensions, and noise from transmission and decoding. In digital systems, most of these artifacts are gone, but we do see blocking artifacts from data compression on occasion. Overall, however, in digital television systems we now have capabilities for HDTV (more spatial resolution), wider color gamuts, non-interlaced (or progressive) transmission and display, more accurate color, surround sound, and the transmission of metadata. It would seem that all of these improvements clearly make digital television systems better than our previous analog systems.

While the transition to digital and HDTV took a long time, it is now past the critical point where large-screen digital HDTV displays are very affordable commodities. In fact, I recently (August 2010), saw flat-panel HDTV sets simply sitting on a store shelf like a loaf of bread. Customers could put them in a cart to take to the checkout themselves. I think that is a sure sign that HDTV has finally arrived (in the USA, anyway).

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Ever wonder ... Can my computer really display "millions" of colors?


Updated: Apr. 19, 2011