August 14, 2017 by cmsturgeon Articles, Exposure, Instructional 0

Understanding the Exposure Triangle

Understanding the Exposure Triangle

The Exposure Triangle;  
What is it, and why should you understand it?

If you have not yet been introduced to this term “Exposure Triangle” or you are yet to master it and definitely desire to do so; I intend on at least making an effort in helping you do just that.

We will start by defining the Exposure Triangle and then go from there. Full Article here

Exposure Triangle:

This term comes from the use of three components / settings in a camera used in combination to accomplish proper exposure.  These three components / settings on your camera are the ISO, the Shutter Speed, and the f-stop.  The Exposure Triangle refers to these three settings used in a way that correspond with each other. In other words, when one changes, at least one other has to change to keep the same exposure.  We will come back to this with examples after giving a brief review of each of these settings within a camera. I have developed an image for a quick glance at what the written content is describing in more detail.  You may want to look at the image various times during your reading of the content.

ISO:

Beginning with the ISO; this is a setting that deals with the sensitivity of your camera’s sensor (when using digital cameras) to light.  These settings are indicated by numbers such as 60, 100, 200, 400 (these are ones normally seen on a roll of film).  With a digital camera, your range of settings are quite a bit wider that the few to select from when purchasing film.

The lower the number, the less sensitive the camera is to light and the finer the grain is.  The higher numbers 400 – 12800 each pick up light no matter how low; and often in turn, give photos that are grainy; depending on how high and what camera you have. For outside shooting on a relatively well-lit day, you will want to use ISO settings of 100 and 200, even on very bright days you can drop to 50 if your camera has this option.

Aperture – F-Stop:

The Aperture settings, also referred to as F-Stop, has a bit more complexity to it than the ISO. When we speak of the Aperture, the basic idea is the opening of your lens.  Unlike the ISO, your numbers seem to go in the opposite direction of what they mean.  An example would be that the more widely open your lens is, the lower the number, the higher number refer to a smaller opening of your aperture.  We call these high aperture (low numerically) and low aperture (numerically high).

In more concrete terms, the Aperture defines the amount of light that can hit your sensor. When we talk about the amount of light, we are also referring to the amount of information.  How that information is interpreted is dependent, in this scenario, on the aperture setting. An example of this would be that of photographing a person up close with a high aperture of f/1.4.  An aperture of this setting would make a portion of the person’s face clear and from that point back all is blurred.  All of that in the background is there, but blurred.  At the same time, being wide at 1.4 will send a large amount of information to the senor making it as bright as the subject.

What we are seeing is that the aperture has control of the amount of light and it has control of how your image(s) are displayed – the depth of field.  Another example would be that of photographing a large wedding party.  In this shot you do not want to single-out one particular person, you want everyone to be crisp clear in the final photo; therefore, you would shoot at a low aperture such as f/28 or f/22.  These will certainly supply you with an image that ensures everyone can be clearly identified.

There are three factors that control you Depth-of-Field.  These are:

#1 – The Aperture setting

#2 – The distance between the photographer and the subject

#3 – The Focal length of the lens

In simple terms, if you are seeking to have bokeh backgrounded images, you should shoot with a high (or wide) aperture – this gives you a Shallow depth of field.  For landscape where all should be clear, shoot with a low aperture (lower numerically).

Keep in mind – high numbers in aperture or f-stops equals complete sharpness and low numbers in aperture or f-stops equals shallow depth of field / blurry backgrounds.

Shutter Speed:

Lastly we come to the Shutter Speed. In digital photography this is what defines how long your sensor sees what is being photographed. I will try to address the important factors relevant to the shutter speed settings.

First, Shutter speed is identified in second or fractions thereof. – The larger the denominator the faster the speed is that your camera allows the “scene” and light in.  (i.e. 1/4000 is extremely faster than 1/100).

Second, your shutter speed selection is not isolated from the ISO and Aperture – they must all correspond and work together.  Your shutter speed can be decided on by the event you are photographing, or the amount of light needed, or the focal length of your lens.

Third, on the matter of your lens focal length. If you are zoomed in on a person at the focal length of 200 and your camera is hand-held, you should not go any lower than 1/200 – I would recommend even faster. If your environment or scenario makes this rule seem impossible to follow, then the use of a tripod is more efficient and practical.

Fourth, the shutter speeds on your camera usually double (approx.) with each setting.  What I mean is that you have a 1/60, then your next is 1/125, then 1/250, and 1/500 etc.  This doubling makes is easier to remind you that aperture settings also double the amount of light that come through per f-stop.  This being the case, when you increase your shutter speed by one, your aperture decreases by one.

Example:  If initial settings are 1/250 with f/4.5 and you decide that you need to increase your shutter speed because of fast movement, then your f-stop should open to f/4 in order to accommodate this change and keep the original exposure.

Fifth, when you are adjusting your exposure, it is a good practice to ask if there is movement within the photo (i.e. a father-bride dance). Then decide how you want this captured.  You may want this to be a “frozen” motion or you may want some motion captured. At an airshow, I found that shooting with 1/1000 was freezing propellers of planes – however, I wanted it to be obvious in the image that the propellers were moving, so I slowed it down to 1/250, yet captured the plane as a still image. The situations you will be in when working with photography can vary from one moment to the next.  One size does NOT fit all!

Sixth, and final point is that some cameras comes with very slow shutter speed options.  If you are using a digital camera that is four years old or less, you will see the option to go down to seconds.  These are excellent for long-exposure shooting and long exposure at night.

A long-exposure example (which definitely requires a tripod) is shown below of a bridge in Chattanooga that is for people to walk on and no longer used for cars.  At night, it is well lit, but not enough to try and hand-hold the camera.  This photo was shot with the exposure (shutter speed) set at 15 seconds.  The amount of time is because the aperture was f/22 in order for all of the foreground and background to be clear.  Additionally, the ISO was set at 400 (usually it would be closer to 8000). The small amount of light allowed via aperture at f/22 and ISO less sensitive require a longer exposure period.  The sky appeared black to the human eye, the longer the exposure, the more the sky lit up.

 

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