A reader who purchased a copy of “Professor Poor’s Guide to Buying HDTV” sent the following comment yesterday:
Your “calculation” of distance from the TV produces impractical results. At 1080p, your calculations indicate for a 42 inch TV you have to sit 5 feet from the screen. It makes no sense!
A lot of people have that reaction, but the fact is that an HDTV needs to be much larger than you might think, especially when compared with a standard resolution television. The real reason that the screen needs to be large is so that you can see the extra detail in the picture. If you don’t need to see the detail, you can save a lot of money by purchasing a lower-resolution panel; from a distance, the image will look the same.
Here’s the proof. Get a standard mechanical pencil with 0.7 mm lead. Get a piece of white paper, and using a magnifying glass, make a dot about the size of the pencil lead diameter. Now make a second dot the same size, spaced about one dot’s width apart. Now, move away from the paper until you can no longer see the two dots as separate items. For me, that’s about six feet.
The pixel pitch for a 42” 1080p LCD is smaller than the pencil lead: less than 0.5 mm. And to really test your ability to “resolve” the dots, you should place two dots adjacent to each other, without the white space between, and move to the distance where you can’t tell if it’s one or two dots. So my test above is a generous approximation of your experience with a 1080p display.
I’m certain that one reason we’re seeing increased sales of larger HDTVs is that the prices have come down, but I think another may well be that people who bought their first HDTV have decided that it is indeed too small, and are now buying a larger one to take its place.
How big a screen do you need for your viewing distance? Find out in Professor Poor’s Guide to Buying HDTV, now available in paperback from Amazon or other fine booksellers.