When the DV format first appeared, in the mid 1990s, it was a massive improvement over VHS. It was a digital video format, which meant an end to tape noise, and the images were so sharp and clear that it was easy to mistake them for those produced on hitherto more expensive 'professional' video cameras. Over the past decade, we have also seen the birth, and blossoming into maturity, of digital still photography.
In some ways, digital still photography is technically less challenging than video, in that you only have to capture a single 'frame' at a time. With video, it's a bit like having to capture 30 still photographs per second, for maybe an hour. In this respect, video is much more difficult than still photography. But in another way, digital still photography is technically more challenging. That's because a video frame has a fixed size (in the US it's 720 by 480 pixels), while in still photography the aim is to capture as many pixels as possible.
In the early days of digital still photography, the number of pixels wasn't an issue. In fact, Sony's first digital still camera, the MAVICA, was actually a single-frame digital video camcorder, which made complete sense at the time because the idea with the MAVICA was that you would display your pictures on a television. There was very little wrong with this idea, as long as digital still photographers accepted that television quality falls very, very short of film resolution.
Fast forward to 2004, and you could buy cameras from any street consumer electronics shop to rival and even exceed the quality of film.
The resolution of digital still cameras nowadays is simply astonishing, as is the technical skill needed to produce CCDs with as many as 64 megapixels, which you'll find in some very high-end cameras. For under $1,000 (US), you can buy a digital still camera with a resolution of around eight megapixels — arguably as good as any non-professional would ever need.
So how does DV resolution compare with this? Well the short answer is, very badly indeed. We can do the calculations quite easily:
A DV frame is 720 by 480 pixels. Multiply them together and you get 345,600 pixels.
That's less than half a megapixel! Half a megapixel is a much lower resolution than even the cheapest digital still camera you can buy today. So how can it be that DV originated video, which looks so good in comparison with VHS, can be based on such a low resolution? There are several answers to this, all of which help to explain the important differences between HDV and DV. When we see an image, our impression of how clear it is depends, in very broad terms, on the amount of information the image presents to us. With still images, the easiest way to describe the information content of an image (short of actually describing what's in the picture) is to talk about the number of pixels. That's where DV loses out in comparison with digital still cameras.
But video has a huge advantage compared to still photography, because with a moving picture the amount of information presented to the viewer is given by the resolution of a single frame multiplied by the number of frames per second! Another way to explain this is to say that video has both spatial resolution and temporal resolution (resolution over time, in other words). Video updates what you're seeing 30 times per second and our impression of the quality of video material is hugely enhanced by this. If it weren't for this effect, VHS quality would be simply unacceptable.
There's another factor as well, which is that we simply don't expect better quality from video. We're used to watching televisions and we're comfortable with the quality they can give. Most people have never even seen how good standard definition television can get. Pictures direct from a studio camera shown on an expensive broadcast monitor look absolutely stunning, and do so despite being constrained to a resolution of less than half a megapixel. So, standard definition television can look great, and will still be around for a very long time. But there are also very good reasons why we now need something better than SD. Here's the main one: big screens.
Big screens present a challenge to standard definition video. The closer you sit to a big screen, the worse it looks, and it's easy to understand why. Quite simply, with a large screen, you need more pixels, not just bigger ones. And that's the problem with standard definition. It doesn't matter how big the screen is, it's still going to be showing the same old 720 by 480 pixels. Bigger screens don't mean more detail, but they might mean pixels the size of dustbin lids.
Despite the inadequacy of our current TV standards, big screens are flying out of the shops. If you ask big screen users what they like about their displays, they'll tell you how flat they are, how little space they take up, and how impressively big they are — but only if they sit a very long way from them will they talk about how good the pictures look.
So big screens are a problem for standard definition TV, although it's not only size that matters. Now that people are used to looking at digital photographs on computer screens, they're starting to ask "Why can't my video look as good as that?" And it's a very good question. Why shouldn't video be available in higher resolutions?
Well the good news is that it is.
Next Section > High Definition Video
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