I found this on another forum, and thought it was great. It was written for film, but it's really good, so here it is. It's similar to the jcoleman sticky, but worded a bit differently. Hope some of you find it helpful. http://www.thephotoforum.com/forum/...-white-film-photography-beginners-primer.html Introduction For some film camera users, the lure of processing and printing their B&W film can become irresistible. This series of articles is designed to ease their path to darkroom competence. This article, and the ones that will following it, are presented as a guide through the various steps - from initial film choice to the mounting and framing of finished enlargements. The general style is "How to" or "Cookbook". In each article, a single path will be outlined in sufficient detail to assure success. For the technically-minded, there will be information on the math, optics and/or chemistry involved. Hints, tips and other bits of information will appear here and there. Every attempt will be made to keep confusion resulting from alternative methods to a minimum. Low cost will be considered in equipment suggestions wherever possible. Once you've followed the procedures in an article and achieved the expected result, you'll have a solid foundation of working technique to use as a basis for further exploration. It's not possible to provide full instructions for all of the different cameras and enlargers currently available, so several assumptions have been made to simplify matters. * It is assumed that the camera used for B&W film can be operated in a manual mode. [We'll mention a way to get around this.] * It is assumed that a 35mm or roll film camera will be used. * It is assumed that the enlarger permits the use of variable contrast filters or has a color head. [We'll explain how to get around this, too.] With that information out of the way, let's cover the first topic . . . Film Choice Note. Correct film choice requires some knowledge of camera shutter speeds, lens openings (f stops) and depth of focus (DOF). That information will be presented in the second article in this series. Many wishing to explore B&W photography already know this material. If you do, skip the second article. If you don't, or if you're rusty, it will help you to understand an important relationship. There are a bewildering number of B&W films available for 35mm and roll film cameras. Some require special exposure techniques. Others require special processing. For now, we'll confine this discussion to films which can be processed in standard developers and fixers. We'll also add the requirement that the films are readily available. You might wish to explore the more exotic films at a later date. By then, you'll be better able to appreciate their special characteristics. Any simple B&W film consists of three layers. The first is the light-sensitive emulsion layer. The second layer is a plastic strip which supports the emulsion layer. The third is an anti-halation layer coated on the back of the plastic strip. The purpose of this last layer is to capture light which has come through the emulsion and plastic layers and keep it from bouncing back -- blurring the image or fogging the film. The emulsion layer contains tiny grains of a silver salt. These salt grains have the amazing ability to soak up bits of light [photons] and, once the light has been absorbed, to react with a developer chemical and break down into pure silver. Until the silver salt absorbs light, though, it will not react with the developer. Each little grain requires a certain minimum amount of light before it will react. Curiously, the entire grain will then react with the developer -- not just the tiny parts of it where the photons struck. For each individual grain, it's all or nothing. This is the key the manufacturers use to make films more or less sensitive to light. If the grains are larger, less light is needed to produce a given amount of silver in the developed image. The film will turn a darker gray than one with smaller grains. It will be a "faster" film, and will produce a useable image with less total light. And of course if the grains are smaller, the opposite happens. The film will require more light to produce the same amount of silver in the developed image. It's a "slower" film. * Film speed is stated as an ISO number. In years past, the letters ASA were used. The actual number is the same. * An ASA 400 film has the same speed as an ISO 400 film. At this point, you may be wondering why it's important to know all this information. There are two reasons: * Faster films are generally "grainier" when enlarged as compared to slower films. * Speed and graininess are the basis on which you choose which film to use for a specific photographic situation. By the way -- as you read through these articles, you'll run into the concept of a trade-off or "give-to-get" more than once. Film speed and graininess is just one example. Commonly available B&W films have speed ratings of ISO 50 to ISO 400. The numbers you will most often see are 50, 100 or 125 and 400. The higher the number, the "faster" the film. Films with higher ISO numbers need less light to form a useful image than films with lower ISO numbers. The difference between 100 and 125 is too small to affect a choice. * A doubling of the film speed number means that the faster film will require only half the light to form an image just as dark as the slower film. This doubling adds up quickly. An ISO 100 film needs half the light of an ISO 50 film. An ISO 200 film needs one quarter the light of the ISO 50 film, and an ISO 400 film only needs one eighth as much light as the ISO 50 film. Another way to say this is that an ISO 400 film is 8 times faster than an ISO 50 film. You can see that the readily available films give you a real difference in performance. The image on a developed negative is made up of silver grains. The larger the grains in the film, the bigger they will appear in an enlargement. If the film is very grainy, the grains will be easily visible as speckling in an 8 by 10 inch enlargement of a 35mm negative. We're almost ready to choose a film now, but first, we should learn two simple "rules of thumb." * Shutter Speed Rule: Don't take hand-held pictures at shutter speeds slower than 1 over the focal length of the lens. The reason for this rule is that we want as sharp a negative image as possible. The longer the focal length of the lens, the more it will magnify any shakiness in our hands as we hold the camera. If the camera lens says 50mm, don't set the shutter to slower than 1/50th second. If you put the camera on a tripod, this rule doesn't apply. You can use much slower shutter speeds as long as your subject doesn't move. That's one of several reasons to use a tripod. Another is to permit you to more precisely examine and "frame" the composition of the picture. * f16 Rule: The correct exposure for an average subject in bright sunlight is 1 over the ISO number of the film, with the camera's lens opening set at f16. This rule allows you to estimate the exposures you'll need with a film based on its ISO rating. For an ISO 50 film, this is 1/50th second at f16. For an ISO 400 film, it's 1/400th second at f16. If your camera's shutter doesn't have exactly the speed given by the rule, just choose the next higher speed. For ISO 50, you can use 1/60 second. For ISO 400 film, use 1/500 second. That's all you need to know at this point to make a film selection. [If f numbers and shutter speeds don't quite make sense yet, they will once you read through the next article. We'll include information on depth of focus in that article, too.] The 50 ASA [slow] films are the correct choice when: * the finished enlargement must have minimum 'graininess', or * the finished enlargement must have maximum detail, or * the light will be strong enough to allow an acceptable combination of shutter speeds and lens openings. The ISO 400 [fast] films are the correct choice when: * graininess is not very important or perhaps even desired, or * the amount of light available will be low, or * shutter speeds must be high in order to stop motion. The ISO 100/125 films are a compromise choice when you don't need either extreme. So, which film? Two commonly available brand names are Ilford and Kodak. Both make 35mm and roll films. The films are of high quality. The ones we recommend are: ISO Kodak Ilford 50: Pan F 100/125: Plus X FP4 400: Tri X HP5 So there you have it. If you're interested in, say, 35mm landscape photography, you'll probably find that Ilford Pan F gives you sharp, fine-grained negatives that you can easily enlarge to 8 X 10 inches. If, on the other hand, you want to take pictures in low light situations or pictures of moving objects where high shutter speeds are necessary, Tri-X or HP5 will be your choice. And if you don't feel that you need either extreme, Plus-X or FP4 are ready to serve your needs. Whichever film you choose, we recommend you work with it long enough to really get to know it. It will become your first standard to judge other films against. The next topic in this series will be shutter speeds, lens openings and depth of focus.