There are two basic kinds of photographic film. First, there is print film, when it's developed, becomes a negative having the colors (or in the case of black & white, having the values reversed), and second, film mounted in cardboard or plastic for projection onto a screen is often referred to as a slide. Additionally, It is often sold as slide film.
The majority of people who shoot SLR using color shoot using color negative film, then have prints made from the film. Rarely do they think about shooting slides...To most, slides are typically a daunting and alien province to them. Woe is them -- shooting slides isn't just for anyone, however it doesn't have to be a horrifying and intimidating concept, either. Shooting slides has distinct advantages...and disadvantages, Weigh the pluses and minuses and come to your own conclusion.
Sales of photographic film have been steadily rising over the last few years, with professionals and amateurs alike rediscovering the artistic control offered by manual processes and the creative satisfaction of a physical end product.
Film Speed Rating - ISO / ASA
All film and digital copies have a speed rating. Digital or traditional, you may see a number labeled ASA or ISO (both denote the film or digital print's rated speed). This ISO / ASA rating determines just how fast the film interacts with light.
Film speed uses stops, just like shutter and aperture
For example, going from ISO50 to ISO200 buys you 2 stops more light. Slower films are less sensitive and generally require longer
exposures / more light. Faster films react rapidly, and can be used in low light situations.
lower numbers = slower films = need more light = longer exposures
higher numbers = faster films = need less light = shorter exposures
*Digital cameras also have a film speed rating, typically around 50ASA. Instead of
purchasing different film for a digital camera, you just change the ISO/ASA, just like "real" film.
Film Speed vs. Contrast and Grain
There's a trade-off between fast and slow films called quality. Fast films typically feature higher contrast and grain. While slower films typically deliver sharper, more detailed images.