Therefore, unless you take a Photography 101 course in college, there is a degree of difficulty picking up the basics of what the modern digital camera is doing with all its present day automation.  However, learning some very basic concepts in photography, aside from light and color, can be very beneficial.  You will soon find that when a photographic situation becomes a bit tricky, being able to get your camera out of that super-auto mode and fly with the stick, to borrow an expression from aviation, will be quite helpful for you, and this is even more true when the creative you wants to emerge.

For a beginner, nothing is more applicable to the basics that need to be learned, than aperture and shutter-speed.  To begin with it’s important to understand that the exposure time and the effective aperture of the lens must together be such as to allow the right amount of light to reach the film (for the old school folks) or sensor. Additionally, the exposure time must be suitable to handle any motion of the subject. Usually it must be fast enough to "freeze" rapid motion; sometimes a controlled degree of blur is desired, to give a sensation of movement, the latter taking some time and practice to master.  But first, you “must” learn the f-stop and shutter-speed concepts.  Be aware that “f-stop” and “aperture” will be used interchangeable here, as in photography they are one in the same… unless you want to get really technical.

Keeping that in mind, a brief and simple explanation of aperture and shutter is that for light to reach the sensor of your digital camera, it must pass through an opening called an "aperture". The aperture is like a pupil. You can control the aperture by setting the "aperture opening", again, also known as an “F-Stop.”   In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor in order to capture a permanent image of a scene. A shutter can also be used to allow pulses of light to pass outwards, as in a movie projector or signal lamp.  The longer exposures ( like 1 second ) give much more light to the film than a 1/1000 of a second exposure. So even though the number may look bigger, don't be fooled!  A half-second exposure is ONE-STOP darker (and faster) than a one-second exposure.  A 1/125 exposure is TWO STOPS brighter than a 1/500 exposure.  A 1/1000 exposure is THREE STOPS darker (faster) than a 1/125 exposure.

Like the pupil in a human eye, the aperture on a camera controls light.  It does so by closing up to restrict light, and opening up to let it through.  Moving from f 16 to f 8 is: TWO-STOPS brighter (f 11 is in the middle).  Moving from f5.6 to f8 is: ONE-STOP darker; moving from f4 to f2.8 is: ONE-STOP brighter, and so on, and so on.

So to understand the balancing act, put simply, between your aperture and the shutter, you can think of it as being about different combinations of shutter and f-stop (aperture) settings to achieve the result of a proper exposure.  However, these combinations can drastically affect the finished picture.  Since f-stop and shutter are both measured or referred to as “stops,” keeping balance is easy. If you take away 2 stops from the aperture, you can give 2 stops back with the shutter (or vice-versa) and end up with the same exposure level.  Meaning, that f 11 @ a shutter speed of 1/125 is the same as (using the “2” stop example, and not one stop) f 5.6 @ a shutter speed of 1/500.  A simple reason of why the photographer might care about this, in case one seems to be the same as the other at first glance, goes back to the stop-action or sports examples.  If you want to freeze action, you need a fast shutter speed, such as 1/125 or preferably faster.  So, having the luxury, you would opt to crank up your shutter speed to freeze or “stop-action,” and then “open-up” your lens, or select a correspondingly lower f-stop (and remember - smaller number, bigger opening).

A more technical explanation would go something like - an optical aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. If the admitted rays also pass through a lens, highly collimated rays (narrow aperture) will result in sharpness at the image plane, while uncollimated rays (wide aperture) will result in sharpness for rays with the right focal length only. This means that a wide aperture results in an image that is sharp around what the lens is focusing on and blurred otherwise. The aperture also determines how many of the incoming rays are actually admitted and thus how much light that reaches the image plane (the narrower the aperture, the darker the image).

Camera shutters can be fitted in two positions: 1) Central shutters are mounted within a lens assembly, or more rarely behind or even in front of a lens, and shut off the beam of light where it is narrow. A leaf mechanism is usually used, 2) Focal-plane shutters are mounted near the focal plane and move to uncover the film or sensor.  Shutters immediately behind the lens were used in some cameras with limited lens interchangeability. Shutters in front of the lens were used in the early days of photography.  Other mechanisms than the dilating aperture and the sliding curtains have been used; anything which exposes the film to light (for a specified time) will suffice.  So, again, the time for which a shutter remains open (exposure time - shutter speed, e.g., 1/500th of a second, or one-second) is determined by a timing mechanism. These were originally mechanical, but since the late twentieth century are mostly electronic.

As for flash photography, which depends hugely on the proper shutter and aperture settings, and this could easily consume an entire article by itself… most shutters generate a flash synchronization switch to trigger a flash, if connected. This was quite a complicated matter with mechanical shutters and flashbulbs (in the old, old days) which took an appreciable time to reach full brightness, focal-plane shutters making this even more difficult. Special flashbulbs were designed in a slow-burn style where the light would reach full intensity, and then remain at that intensity to wait for the slow focal-plane shutter to expose the full film frame. Many of these problems have been alleviated with modern electronic timers and electronic flash units which fire virtually instantaneously and are managed by sophisticated algorithms within the flash and camera, in some cases. When using a focal-plane shutter with a flash, a photographer will typically operate the shutter at its X-sync speed or slower; however, some electronic flashes can produce a steady pulse compatible with a focal-plane shutter operated at much faster shutter speeds. Keeping in mind that the focal-plane shutter is still going to impart focal-plane shutter distortions to anything that is moving.

Happy Shooting!

Richard Seymour

JarGra Photographic Art