Our very first monthly newsletter (September 2008) included a brief look at megapixels and how they relate to digital image resolution. Well, it’s now almost two years removed from those early Tech Tip days and times have changed. Well, not all that much, really. But, enough has changed that makes it worth an updated look at pixels, this time from a video and film perspective.
We’ve discussed HDTV and other forms of high definition video previously. As a quick refresher, HDTV is broadcast in two formats - 720p and 1080i. 720p displays sixty 1280 x 720 progressive frames per second and works best for sports and action or anything with a lot of motion or camera movement. 1080i displays thirty 1920 x 1080 interlaced frames per second and is best for nature, drama and other general TV programming. Keep in mind that most HDTVs sold today have a video display that presents all footage as either 720p or 1080p; this means that the incoming broadcast signal may need to be downscaled, upscaled or de-interlaced before being displayed on your screen. This can cause a decrease in image quality for all formats except for 720p on a 720p screen. I tend to prefer the 720p broadcast format because 720p upscaled to 1080p looks better to me than 1080i de-interlaced and reconfigured as 1080p. So why is 1080p considered the best? Blu-ray, my friend. Blu-ray discs are almost exclusively produced in 1080p and look awesome on a 1080p (or 720p) display.
So, what about digital projection in a movie theater? To begin, be aware that about 16,000 of the 32,000 movie theater screens in the U.S. have converted from film projection to digital projection. Film projection isn’t tied to a specific resolution because the image you see on the screen is created by a beam of light passing through a frame of film; it’s an optical process, not a digital one. In essence, 35mm film’s only resolution limitation is the grain structure of the film emulsion. If you continue to enlarge the projected image of a film frame, you will eventually begin to see more and more grain structure and, at that point, which will be different to viewers at varying distances, the film will have reached it’s resolution limits. More on that in a moment.