There are over 2700 photographs taken every second around the world, adding up to well over 80 billion new images a year taken on over 3 billion rolls of film, according to estimates published by the United States Department of Commerce.
Photo CD, a format for digitized photography introduced by Kodak in 1992, has been widely adopted both by professional and amateur photographers. Kodak reports that the typical photograph can be digitized in this format in 5 megabytes without loss of picture quality. Utilizing this conversion factor, then, the world's 82 billion photos store 410 petabytes of data every year in photographs.
Apart from still photography, film is also used to store moving pictures. In the years from 1990 to 1995, UNESCO reports that there were 4,250 films produced annually throughout the world. The Motion Picture Association of America reports that for the year 1998, its members released 221 movies (compared to 219 in 1997), while releases by all U.S. companies, including independent film companies, rose from 461 in 1997 to 490 in 1998.
It takes approximately 2 gigabytes to store an hour of motion picture images in digital form using the MPEG-2 compression standard. If the images in 4500 full length movies were converted into bits, the world's annual original cinematic production would, therefore, consume about 16 terabytes.
The other major use for film is the storage of x-ray images for medical, dental and industrial purposes. Approximately 2 billion radiographs are taken around the world each year, including chest x-rays, mammograms, CT scans, and so on. (Traditionally, 8% of x-ray film is used in dentistry and industrial applications.) When x-ray films are converted to digital format, it is important that there is no important clinical information lost. The University of Pittsburgh Clinical Multimedia Laboratory suggests that an average conversion of a chest x-ray to digital storage with lossless compression will require 8 megabytes. To store all the world's x-rays to a computer file of this size would, therefore, require 17 petabytes each year.
The number of original photographs stored around the world is not a widely reported topic. There are commercial firms that collect professional photographs for resale and the largest of these report collections in the tens of millions. For example, Getty Images reports holding 70 million images mostly on silver halide film and its principal rival, Corbis Images, claims 65 million images.
As for amateur photographs, in 1997 it was estimated that there were 150 billion photographs stored in the United States. This is approximately 8 to 10 years production of photographs as of that time. Assuming that similar storage rates apply worldwide, it is likely that on the order of 750 billion photographs now exist. Using the same PhotoCD estimate of 5 megabytes per photo, there are 3.5 exabytes of original photographic data.
The number of motion pictures made around the world from 1895 to 1990 was approximately 242,000. The International Film Index, 1895-1990, lists entries of that many titles of films. (There is no guarantee that some of these movies still exist, however.) The overall total is broken down into these categories of film types:
The "Television" category refers to films that were originally made for television broadcast rather than theatrical release. "Serials" are films made primarily in the United States between 1914-1936 and were made to be shown in weekly installments.
As discussed in the precedng section, in the decade since 1990, there have been around 4500 movies made each year, adding another 45,000 to the total world stock of original motion pictures. Accordingly, a good estimate of the world's original pictures is approximately 300,000.
The clinical and legal uses of medical x-rays continue for an indefinite time and, therefore, prudent practice is to preserve x-rays and medical records generally for as long as possible. The same principle applies to dental x-rays. The only use of x-ray that may result in regular destruction of the resulting images is industrial testing, but even there it is likely that images are retained for a substantial period of time. Therefore, it is believed that there is little systematic destruction of the flow of new x-rays and virtually all of them are added to the stock. For the sake of calculation, it is assumed that a full ten years of x-ray images will constitute the stock. This is equivalent to approximately 21.6 billion images or 172.8 petabytes.
There has been very little history of the large mass of photographs being copied. Kodak estimates that only about 2 percent of photographs are ever copied or modified in any way after they are originally developed. Of course, some photographic images are widely distributed in newspapers and magazines. But these represent a miniscule fraction even of the professional photographer's work, itself a small minority of all photographs.
One copy of 2 percent of the annual new photographs would be 1.6 billion photographic copies. With PhotoCD compression, this would represent 8 petabytes per year of photographic copies.
The Wolfman Report on the Photographic and Imaging Industry in the United States states that the average number of prints per original motion picture is 700. The Silver Institute, however, reports that 6000 release prints are made for each feature movie. A figure of 1000 copies for motion pictures will be used on the assumption that many of the world's motion pictures have more limited releases than the typical Hollywood blockbuster. American studios only account for 400 to 500 movies per year. 45,000 copies of motion pictures per year at 4 gigabytes per copy is 18 petabytes of copies.
The clinical requirements for medical x-rays demand that originals be used in almost any situation. There is no siginificant use of copies of x-rays at all.
The stock of copies of photographs can be calculated by reference to the assumptions made for the storage of the originals. Ten years of copies of photographs would be 16 billion. If these were all digitized at the rate of 5 megabytes per picture, there are 80 petabytes of photographic copies on hand.
The copies on film of motion pictures made for distribution are short-lived. Most of these copies are deliberately destroyed when the general theatrical release of the movie is over. If even ten of these survive for the approximately 4,000 motion pictures made annually for the last twenty-five years, this would be equivalent to about 1,000,000 copies. If each copy is equivalent to 4 gigabytes of data, this stock of copies of motion picture film is 4 petabytes.
There is no significant stock of copies of x-rays.