Types of Color Film
In digital photography, there is essentially only one kind of film. You could say that file formats differ widely, such as RAW, JPEG, and TIFF, but this is just a software issue.
You could also say that high-speed CF cards are much different from memory stick media. However, they both store the same information, so again, it's not a real difference. Slide film, however, works much differently from negative film. The differences reveal advantages and disadvantages to each format.
Negative film produces an image that is the opposite of the original scene in color and density. It can be printed on paper in a darkroom to make a positive or scanned into a computer for editing and printing. It is usually easier to work with negative film if the final medium is a print. Color negative film has a considerable tolerance for under- and overexposure (exposure latitude), and, when scanned, is superior to reversal film for photographs of very contrast-laden scenes.
Reversal Film (Slide Film, Transparency Film, or "Chromes")
Reversal film can be projected for viewing, printed on reversal paper in a darkroom, or scanned into a computer for editing and printing. Reversal film requires more precise exposure than negative film because it has less exposure latitude; errors in exposure or color balance may be difficult or impossible to correct in printing.
However, reversal film has advantages in cost and convenience over negative film, and images can be viewed directly. Reversal film, especially in large format sizes, is almost universally preferred by professionals because its images will be reproduced by offset printing presses. Reversal film often has "chrome" in its name (Agfachrome, Ektachrome, Fujichrome).
Sometimes the word "professional" in a film name is merely a marketing strategy. For color film, however, the word bears a little more weight. Professional films, for example, have exposure latitudethe amount of underexposure or overexposure they're capable of handlingthat is much smaller than consumer-type film. In addition, they are much more sensitive to temperature shifts. If you decide to experiment with professional film, store it in a refrigerator to retard aging and keep the color fidelity constant.
Negative or reversal "professional" film also is designed and manufactured for professionals who demand accurate color balance. A film's age and its ISO rating and color balance change during storage. Professional film is shipped with its qualities near their peak, and is refrigerated by camera stores to ensure that it is in the best condition.
Professionals usually buy large quantities of film, preferably all from the same manufacturing batch, and they shoot test rolls to determine its precise ISO and color balance. Professionals keep film refrigerated until it is used, and develop it as soon as possible. Conversely, amateur film may be shipped before it is ready, as the manufacturers anticipate that it will not be used immediately. It often improves after a few months of room-temperature storage.
The useful life of unopened film can be extended by refrigeration or freezing. However, once film is opened (you take it out of its plastic container), it is better kept at room temperature and should be exposed and developed promptly.
Films for Specialized Color Balance and Exposure Times
Each type of color film is intended for a specific type of light. Ordinary daylight film is color balanced for daylight and electronic flash. Type B tungsten film is balanced for 3,200° Kelvin (or K) studio quartz-halogen lights, although ordinary incandescent light bulbs are acceptable. There are a few films for special situations: Type A film is made for 3,400° K lights. Type L (for long) negative films are designed for long exposures (60 to 120 seconds) under tungsten light.