FORMAT WARS

How does Video, Digital, HD, and Film compare? How are these formats different, and how are they alike? Which is the best, which is the cheapest.....and so on?

Let me start by saying it is a common misconception to confuse Analog Video with High Definition Video, and to think they are more or less the same, or a very similar thing. In fact, people often confuse the general family of formats known as Digital Video, as being basically the same thing as Analog Video. Often the term 'Video' and 'Digital' are used interchangeably. It is true that 'Digital' and 'Video' have a common heritage, however, the differences can be so great that 'High Definition Digital' can be considered a new format in its own right with its own unique characteristics.

While 'Analog' and 'Video' tends to be quite similar for the various Standard Definition Television formats (SDTV), this doesn't hold true for the High Definition formats (HDTV). For example, mini-DV or DVCAM are more or less digital versions of analog Betacam SP, and the overall quality and general look of the image is very similar. In fact, most people can't tell them apart if you don’t look too closely at the different artifacts in the image. So in this case 'Digital' and 'Video' are pretty much the same thing i.e. they more or less 'look' and 'feel' the same.

But things begin to change in the High Definition world. For one thing, there is not really any Analog High Definition formats (although an Analog High Definition format has been used in Japan). But for all practical purposes, all High Definition formats these days are Digital formats. Digital High Definition has characteristics common to both Analog Video and 35mm film. In terms of the general look and the feel of the image, it is much, much closer to 35mm film than the old-fashioned analog formats!!! For this reason, it can be considered in its own unique category...definitely not like Analog Video, and much more like 35mm film. It has its own look and feel, and its own unique characteristics not found in either Analog Video or film.

So (1)Analog Video, (2) High Definition Video, and (3) 35mm film - are really three very distinct formats, with their own look and feel, advantages and disadvantages and so forth.

Which is the best quality - 35mm Film or High Definition digital video? This of course, is a difficult and somewhat controversial issue to answer.

Very broadly speaking, the current film and HD technologies are about the same in terms of range and quality, or more or less on a par with each other. But film is still significantly better than HD in terms of overall resolution. Film has more image forming elements (grain) compared to current HD images (...now around 2 million pixels or picture elements).

However, film loses a lot of its advantage in terms of resolution, because of the film weave phenomenon. Film is always weaving and moving about during shooting, printing, and projection. This reduces film’s inherent resolution considerably, so much so, that lower-resolution HD images can compete fairly closely with film in terms of overall image quality. If a film frame could be kept perfectly still (like with HD), a film image would far surpass a HD digital image in terms of resolution. But comparing a 'static' HD image, next to a film image with its inherent weave and movement, they look to be of similar overall quality and resolution to most observers (although, technically, film is still better, in an absolute sense).

The main differences tend to be in the artifacts, peculiar to each medium. In addition to the often quite noticeable movement when projected on a big screen (especially with text - like titles and credits on screen), film prints are more likely to be scratched or dirty, are more prone to the effects of strobing with any sort of movement (both within the frame, or with pans and other camera movement etc.). While digital HD tends to be cleaner and brighter on the screen, and definitely more static or stable, although pixilation effects, compression effects, and similar digital artifacts may be noticeable in certain circumstances.

Digital technology has to do one, of two main things, to catch up, and surpass, film technology. Firstly, increase the overall resolution by putting more pixels on the CCD. This can be easily done right now, by simply making CCD’s bigger. Instead of using a Super 16mm-size CCD like in the current Sony HDCAM cameras, use a CCD closer to the size, or the same size as, a 35mm frame. This can be done right now, and has also been done in the past with earlier HD systems. It is not a question of technology, but rather a question of cost. The bigger CCD could double the overall cost in making a higher resolution system. And this is, generally speaking, not considered acceptable from a marketing point of view. But the cost might come down, and/or the marketeers might change their strategy in the future.

Secondly, and this is a much more difficult technical issue, is to find a much faster and higher capacity methods of storing digital data streams, compared to (now almost) old-fashion video tape. A lot of the potential HD image quality is lost by reducing the data rate, and also by using various lossy compression schemes, to reduce the size of the overall data stream sufficiently so it can fit onto ordinary video tape. The video tape itself seems to be the weakest link in the chain with current HD technologies, as it tends to limit the potential quality of the overall system.

A major advance on either of these technological fronts, could easily put HD technology ahead of film technology, virtually overnight. Just one technological advance could deal a blow to film so to speak, and both technological advances might be the equivalent of a mortal blow perhaps? And based on recent historical trends, there is no reason to think this wont happen quite soon (perhaps in as little as a year, or so). Already, the German Arriflex company is experimenting with making a fully digital camera with a 35mm-sized CCD. And Sony has made cameras like this in the past, which produced spectacular images that looked easily as good as film in many respects.

After all, film is rather old technology developed in, what is now, the century before last. It has served us well, and still continues to do so....but maybe it is time to take the next logical step, and look forward to an even better, more versatile system for the future.

WILL THE REAL DIGITAL CAMERA PLEASE STEP FORWARD!!!

Here is perhaps a great irony in the world of film and video. Things are not necessarily what they seem. In essence, a film camera behaves much more like a digital camera, while a digital camera is really analog at its core!!!! A film camera is perhaps the true digital camera, and all the rest are analog cameras!!!! Can this seaming contradiction be true?

Lets look at how a film camera and a digital video camera 'capture' their respective images. We need to compare them right where the image is actually formed - within the film emulsion, on the one hand, and inside the video CCD, on the other hand. In both cases it is an interaction of light and chemistry.

Film has millions of silver halide crystals suspended in an emulsion. In a sense, this random array of silver halide crystals is similar to the more regular array of pixels in the video world. If an individual silver halide crystal is stuck by light during the exposure period, it will chemically change to a metallic silver deposit during the subsequent processing or development of the film. Any silver halide crystals not struck by light will not change during the normal chemical development process. So each individual silver halide crystal either deposits as silver, or doesn't deposit as silver, as the case may be......there are no in between states. Just silver, or not silver. This is just like the 'on' or 'off', 'high' or 'low', 'positive' or 'negative' states utilized in the digital world i.e two distinct states. During the exposure period, a film camera turns its pixels or grains in the film emulsion, either 'on' or 'off'. This is the basis of all digital technology and processes.

By comparison, lets look at what happens in the CCD of the digital video camera? When light strikes an individual pixel element, it produces electricity. The stronger the light, the higher the voltage output; the less strong the light, the lower the voltage output. In other words, the output of the CCD is pure analog!!! It may come as some surprise to learn that all CCD’s are analog devices!!! In all digital cameras, the analog signal that is output from their CCD’s, then has to be digitized in a later step i.e. after the essential image information is formed and captured. At its heart, all digital cameras are analog!!!

But this is where the analogy ends. After the digital-like capture of the film image, all subsequent process are analog in the film world. And after the analog capture of the digital video image, all subsequent process are usually (or mostly) digital in the digital-video world (although it might be converted back to analog for display purposes, and so forth).

Film is a photochemical process; the video is photoelectric. All, so called, 'digital cameras' in common use today, are essentially analog cameras. Perhaps ironically, if the silver halide and silver deposits in a film emulsion could be converted to an electrical signal somehow, then a film camera would be the ultimate digital camera!!!

Peter Gray
(near Los Angeles)
P.O. Box 5132
Pine Mountain Club, CA 93222
United States of America
telephone: +1(661) 242-1234

dp@petergray.org