September Q&A

Q: What type of gelatin is used in the manufacture of photographic film? Is synthetic gelatin used?

A: Gelatin is critical to photography, as we know it. Before gelatin came into use, photography was very difficult, time-consuming, and expensive because of the processes that had to be used. However, once gelatin became the medium in which the silver halide crystals were precipitated and the medium coated onto the glass or plastic support, photography became practical for use by the public. Gelatin, a naturally occurring polymer, is a long chain composed of a number of different amino acids. These chains interact with the silver ion and the silver halide crystal during crystal formation and growth so that the silver halide grains grow as individual grains and do not clump together. During the coating operation, the gelatin solution with the silver halide grains and any other photographic chemicals is gently warmed at which point it has a low viscosity and flows quite freely. However, immediately after coating, the material is cooled, actually only a modest drop in temperature, and the solution "gels" or forms a layer that does not flow. This allows the coating of photographic products at relatively high speed and the coating of many different layers on top of each other without mixing during the coating operation. At the time of coating hardeners are added to the solution so that after the coating step, the layers will become hard enough that they will not dissolve during the processing of the exposed film. Gelatin also has the property that the hardened gelatin layers will swell when wet and allow the processing chemicals into the layers so that the development reactions can occur, but the layer structure remains intact. Because no other synthetic materials have been found that have all of these properties, gelatin has been used in the production of photographic products for over 100 years.

The gelatin used in photographic products comes from the bones and hides of pigs and cattle. Gelatin is manufactured from the protein collagen. The exact manufacturing process used depends on the properties the gelatin needs to have. The hides or bones are soaked in an acidic or basic aqueous solution for a period of time ranging from hours to months followed by a gradual increase in temperature to extract the gelatin. The gelatin solution is then drained and washed. After the pH is adjusted, the gelatin is filtered, clarified, concentrated, and dried. In some cases the gelatin is chemically treated some more. The gelatin used by Eastman Kodak in its photographic products comes from a subsidiary company, Eastman Gelatine Company (www.eastmangelatine.com). Eastman Gelatine produces gelatin for the imaging, pharmaceutical, and food industries. The gelatin produced for the imaging industry is the highest purity gelatin produced because of the sensitivity of the silver halide crystals to any chemical impurities.

Q: How can one have film images converted to a DVD?

A: If you are an amateur with home film movies that you would like to have transferred to a DVD, Eastman Kodak does not provide this service. However, there are several ways one can transfer one's home movies to a DVD. The methods vary from very inexpensive to very expensive. The very inexpensive way is to project the movie onto a white wall or screen and use a DVD camcorder to capture the projected movie. The DVD that comes out of the DVD camcorder is the DVD one would want. Some people have old movies, but do not have a way to project them. In this case if one types "film to DVD transfers" into any search engine, one will be given a very large number of hits. There may be a company relatively close to where one lives or one may want to use a mail-order service. The lowest cost transfers will be using the method described above - project the movie on the wall and capture with a DVD camcorder. The most expensive transfers will be done in a post-house with a telecine. The quality and options on the DVD creation will be reflected in the cost of the transfer.

Q: How are the DVDs of theatrical releases made?

A: The DVDs from the studios of the major movies are not produced in the way described above. Most movies shown in a theater are shot on film. But that film is not directly printed onto print film as was done years ago. Instead, the camera negative film is scanned, a process that produces a digital copy of the information on the film. That digital copy is modified by the creative people working on the movie until the exact look is achieved for every scene in the movie. For theatrical release that modified digital movie is recorded to intermediate film, printed onto the print film, and distributed to all the theaters around the world. However, that modified digital movie can be down converted to a video format. This video version of the movie may be further manipulated by the creative team because of the differences between the colors film can make and the colors a television can make. The video version is then processed in a computer through a two-pass process. In order for the entire movie to fit on a standard definition DVD, the movie has to be compressed. But for optimum quality, the minimum amount of compression is desired. Therefore, the first pass looks at the movie and decides how to compress each image in the movie. Because the DVD can hold 4.7 G of data, the computer adds up the size of the compressed movie after the first pass and calculates how much more or less compression is needed in order to exactly use the storage on the DVD. The introductory frames, title frames, or any other frames that will go on the DVD must be included in this calculation. Then the second pass goes through the movie encoding it based on the results of the calculations from the first pass so that the entire movie will just fit on the DVD. Finally a DVD glass master is made. This glass master is very hard and durable so that it can be used to make the multiple copies of the movie. The DVD copies are made by simply pressing the glass master into the DVD disk. In this way, thousands or millions of DVDs can be made of one movie.