What is the difference between film speeds (e.g. ISO 200)?
ISO 100 is the slowest (i.e. least light sensitive) film speed most amateurs would use. It is good for bright, sunny days and results in sharp images with very little “grain” (i.e. spots in the image detail caused by the shape of silver crystals in the film emulsion.) As this is a slow film speed, you are more likely to get underexposed photographs or camera shake (due to the slow shutter speed required to gain a good exposure.) As film technology has advanced, most people are now using ISO 200. This is twice as sensitive to light as ISO 100, but still offers minimal grain. It is good for most situations. ISO 400 is the fastest film most amateurs would consider using. It is good for poor lighting situations or indoor shots where a flash is used and the subjects are quite far away. It is also good with zoom lenses as a faster shutter speed can be used – zoom lenses magnify the effect of camera shake (in the same way that when you hold a long pole out in front of you, the end of the long
