Aperture is measured using F-Stops
. F-Stop numbers represent a fractional formula representation of the amount of light allowed to pass through the aperture. In simpler terms, F-Stop numbers get bigger as the aperture gets smaller, just like shutter speed numbers get bigger as the time the shutter is open gets smaller. Each increasing F-Stop number roughly represents a halving of the light reaching the film. As the aperture closes, more of a scene will come into focus as well (as we learned in the depth of field lesson
F-Stop Relationship to Light and Depth of Field
- Big F-Stop Number = More Light Needed = Larger Depth of Field
- Little F-Stop Number = Less Light Needed = Less Depth of Field
Many photography texts over the years have attempted to drill the idea of small aperture = large F-Stop into new photographers' brains. While this is important to know, I have seen far too many new photographers become discouraged trying to remember this inverse relationship in the field. If it is easier for you to remember the F-Stop relationship to light and depth of field then by all means, use the memory method that works best for you in the field. If you miss a shot because you are trying to remember the aperture to F-Stop mechanics then it is just a hindrance.
While there is actually a huge range of F-Stops (aperture sizes) possible, depending on your lens, there is a common ground middle range that most consumer lenses are capable of operating within.
Common F-Stop Values