Exposure = Shutter + Aperture + ISO

The first key to successful photography on your Disney vacation is to understand the basics and dynamics of photographic exposure.  Before you learn anything else, you need to know how a photograph is made so you can understand how to alter the process in order to achieve better results based on the subject matter at hand.  Consider the depiction of the “Exposure Triangle”:

exposure-triangle

EXPOSURE is the total amount of light allowed to fall on the photographic medium (photographic film or digital image sensor) during the process of taking a photograph.  It is determined by three variables:  SHUTTER, APERTURE, and ISO (film speed).  Think of this as a three sided triangle; when one side changes, one or both of the other sides must change accordingly to maintain the same exposure.

The SHUTTER is similar to the shutters on your home.  When your shutters are closed, no light is entering your windows and your home remains dark, even those the sun is shining outdoors.  When the shutter on your camera is closed, no light enters the camera even though light is entering the lens.  When the shutter is open, light enters the camera through lens and strikes the previously mentioned medium, causing an image to be recorded.

Shutter speed refers to the time in which the camera’s shutter is open, and is expressed in terms of time, such as 1/60 second, 1/125 second, etc.  It is usually shown on the camera as a whole number, such as 8, 60, or 125 (referring to 1/8, 1/60, or 1/125 second respectively).  In the event of shutter speeds slower than one second, the camera usually shows the number with a quotation mark, such as 3” for 3 seconds.

Generally speaking, shutter speed is expressed in a series starting from one second and doubles or halves depending on whether you are getting faster or slower along the way (15″, 8″, 4″, 2″, 1”, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, etc).

Each step along the way represents one full STOP; each stop represents a halving or doubling of the light being captured.  For example, 1/30 second captures two times as much light as 1/60 second.  It is not uncommon to have speeds of at least 1/500 second in bright sunlight.  Fast shutter speeds (1/500 second) are imperative when the subject is moving or you are moving (Lights, Motors, Action Stunt Show).  Slow shutter speeds (1/30 second) are necessary when light levels are lower, such as on a dark ride.

The APERTURE is the part of the lens that decides how much light enters the camera.  It can often vary in size depending on the scene being photographed.  It is very similar to the pupil in your eye.  When the pupil is dilated (wide open) more light enters your eye. This is necessary for you to see properly when light levels are low.  When the pupil is constricted (small), less light enters you eye, such as when it is bright and sunny outside.

Aperture is also known as the “f-stop” and is expressed by a series of numbers such as f/5.6.  In an ironic and confusing twist of fate, the larger the number, the smaller the aperture and smaller the number the larger the aperture.   Small  number = big hole and large number  = small hole.

The series of numbers are based on a sequence of f/1.0 and f/1.4, which alternate and double to produce the rest of the sequence (f/1.0, f/1.4, f/2.0, f/2.8, f/4, f/5.6, f/8, f/11 and so on).

Each step in the series in either direction is also known as a stop, and represents a doubling or halving of light being captured from the next or previous number.  Another example of this would be a hose.  A four inch hose would allow twice as much water to flow through as a two inch hose.  Changing from f/4 to f/5.6 is one stop, and f/5.6 captures half the light as f/4, and f/4 captures double the light from f/5.6.

Lenses with wide apertures (lower maximum f-stops) are known as fast lenses, such as f/2.8 and lenses with smaller apertures (bigger maximum f-stops) are known as slower lenses.

Finally, ISO (similar to film speed) changes how sensitive the senor or film is to light.  This is expressed in terms such as 100 speed, 200 speed, 400 speed, etc. in film and ISO 100, ISO 200, ISO 400 etc. in digital.  Once again, each step in the series represents a doubling or halving in sensitivity, known as a stop.  400 speed is 2 stops ‘faster’ than 100 speed, and would therefore be impacted by four times the amount of light.

iso-chart

Now that we have identified the three sides of the triangle, let’s see how they affect each other.  Let’s take our imaginary triangle; the following combinations of settings would be nearly equal (the numbers in parentheses represent the increase or decrease in exposure value needed to maintain the same overall level):

ISO 100, f/4, 1/60

  • ISO 200 (+1)     f/5.6 (-1)     1/60 second (0)
  • ISO 200 (+1)     f/4 (0)     1/125 second (-1)
  • ISO 100 (0)     f/5.6 (-1)     1/30 second (1)
  • ISO 100 (0)     f/2.8 (+1)     1/125 second (-1)
  • ISO 800 (+3)     f/4 (0)     1/500 second (-3)
  • ISO 400 (+2)     f/2.8 (-1)     1/125 second (-1)
and so on and so on…

All of these combinations of settings would produce a nearly identical exposure, with minor differences in depth of field and sharpness.  There are many other possible combinations that would yield the same result; you need to know when to use certain combination of settings to accomplish your goal.

The key now is knowing how to apply the proper exposure to the situation at hand.  If you want to photograph Cinderella Castle during the day, any of the above combinations would work. If you are photographing SpectroMagic at night when the area is dark except for the floats, you will need to use the higher ISO and smaller aperture to get a fast enough shutter to “stop the motion” of the floats.  In other words, you need to set your camera to be able to handle the exposure much faster than it would probably like to because if you do not, you will have a blurry photo due to motion blur.  If you are using a tripod for a night-time photograph of Spaceship Earth, use the lowest ISO and a fairly small f/stop such as ISO 100 and f/8 to get the highest quality photo.  In this instance, due to the luxury and non-moving subject, you have the luxury of being able to take a much slower, high quality exposure.

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