Understanding Manual Exposure Control of Cameras: #
(Before we start, go get your camera and have it next to your to refer to as you read. If you need your owner’s manual to help you locate the controls, get that too.) #
Exposure is the amount of light that hits the camera’s sensor or film. #
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We will now begin photographing using manual mode. (If you need to, see the owner’s manual for your camera.) In order to truly master photography, you must begin by shooting in manual mode and work to understand the ramifications of aperture and shutter speed selections you set into your camera. To do this, we are not going to rely on the built-in light meter in your camera. Instead, we are going to use basic knowledge of how powerful light is in certain situations. We need to determine a method for selecting which f-stop (aperture) and shutter speed combination we will use to get exposures you want. The method is called The Basic Exposure Formula (BEF) and is discussed in greater detail below. First, we have to define what f-stops and shutter speeds mean and develop an understanding of their relationship to one another. They will be our primary tools for controlling exposure without relying on our camera metering systems. There are two primary variables that control how much light the film will receive:
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(There are actually three variables, the third being ISO, or “film speed,” but we won’t address this third variable until Lecture # 2.)
These concepts will be explored in more detail later. For now though, we will not use our camera meter but will use the BEF to determine the correct exposure. You will start out by first setting your camera to a manual (M) mode. This mode will bypass any information sent from your camera’s internal meter allowing you to set both the aperture and shutter speed.
Let’s start with apertures and how they control the amount of light coming into your camera lens and then move on to shutter speeds, which control how long the shutter in your camera is open.
Aperture #
Apertures: The aperture is simply the size of the opening that lets light through the lens.
The number for the aperture that you will set is called an f-stop. It is a fraction that relates to the actual size of the lens opening. For the rest of this course, aperture refers to the size of the opening in the lens, while f-stop is number that you set. The number represents a fraction and is displayed like this: f/2 or f2. It translates into a fraction by replacing the f with a 1, we see these f/stops actually refer to 1/2 and 1/8.
Since we can put different lenses on our cameras (or select different focal lengths on a zoom lens) it is necessary to express the actual size of the aperture opening in relative terms; thus f/2 instead of 1/2. To take this further, if you had a 50mm lens on your camera and you set your aperture to f2, you would be setting an aperture diameter of 25mm (1/2 of 50mm = 25mm). If you selected f/2 on a 100mm lens that opening would be 50mm in diameter (1/2 of 100mm = 50mm). F/2 on a 300mm telephoto lens would have aperture with a 150mm diameter, and so on. Because the f-stop should be considered a fraction, i.e. f8 can be considered 1/8 and f2 is 1/2, we can better understand why f2 is a larger opening than f8 as 1/2 is larger than 1/8.
Viewing the aperture diagram above, we see that when the aperture gets smaller and lets in less light, the f-stop number gets larger. While f8 may seem like a larger number than f2, we now know that f8 hole is smaller and lets in less light.
Apertures range in f-stops from f/1 to f/64 in one-stop increments. A one-stop increment either doubles or halves the amount of light hitting the sensor. The whole f-stop number range is listed below. You will be responsible for committing these whole f-stops to memory.
1 • 1.4 • 2 • 2.8 • 4 • 5.6 • 8 • 11 • 16 • 22 •32 • 45 • 64
Shutter Speed #
Shutter Speed: The shutter speed is the time that the light coming through the lens is allowed to hit the sensor. This time is based on how long the shutter inside your camera is open. The shutter speed numbers are primarily based on fractions of a second, though you are able to dial in full seconds too. Below is an example of a shutter speed range in full stops. Full seconds are listed on the left down to 1 second. As you move right the numbers show fractions of a second.
30s • 15 s • 8 s • 4 s • 2 s • 1 sec • 1/2 • 1/4 • 1/8 • 1/15 • 1/30 • 1/60 • 1/125• 1/250 • 1/500 • 1/1000 • 1/2000 • 1/4000
Obviously, the longer the shutter remains open the more light that can pass through the lens. Therefore the larger the number you dial into your camera, the faster the shutter speed. The shutter works by opening for a specified length of time and then closing.
The SLR camera, especially 35mm cameras, usually have what is called a focal plane shutter as shown above. The shutter speeds usually start from around 5 – 30 seconds on the slow side up to 1/4000th of a second for certain cameras.
When speaking apertures we do not mention the fraction, e.g. 1/8. But usually when speaking about shutter speeds the fraction is mentioned. 60 on the camera means 1/60th of a second. Some digital cameras with LCD’s will actually write the shutter speed as a fraction. Oftentimes on a camera, the shutter speed dial, shutter speeds over one second are in a different color.
Just like the apertures, full stop adjustments of the shutter speed will allow either twice as much (2x) light, or half (½) as much light to the sensor.
Take a moment to identify the aperture and shutter speed dials on your camera. You can confirm which is which by comparing both to the listed numbers above.
Please note:
- Your camera may not show the full range listed, this is fine as long as you have five full stops to work with. This means you will have five of the numbers listed above for each. If the camera you are using does not have this, please let your instructor know.
- There will be other numbers (usually two) in your camera between the full stop range numbers listed above. This is great as they will give you more exposure control. Starting out we are going to make it easy and work with full stops.
Learning to Use the Sunny 16 Rule: #
Because exposure is the most important aspect of photography, it helps to start with a general guideline for determining the best exposure. The Sunny/16 Rule is a guideline used for determining correct exposure for film or digital cameras without relying on a light meter.
Note: The Sunny 16 rule is also known as the Basic Exposure Formula here at SBCC and is often shortened to BEF. As photographers outside of SBCC have not heard of BEF, I prefer to call it the more well known Sunny 16.
This rule states that when creating a photo in direct sunlight, the correct exposure will be:
- 1/ISO @ F16
What does this mean exactly? #
This means that when shooting outdoors in direct sunlight, you can set your aperture to f/16 and adjust your shutter speed according to the ISO setting on your camera. Every digital camera has an ISO number that has to be set on the camera. The ISO references the sensor’s sensitivity to light. Every sensor needs just the right amount of light for a correctly exposed photograph. Too much light and photo is overexposed (too bright). Too little and it is underexposed. (too dark.) The total amount of light hitting the sensor is determined by two settings on your camera, the aperture and the shutter speed.
If you are shooting with your camera set to ISO 1000, then your exposure will be 1/1000 @ F16, if you set it to ISO 100, your exposure will be 1/100 @ F16.
Now, because this is a beginner course, you are required to use the Major Scale of Exposure Settings. Meaning, that instead of using 1/100 as a shutter speed, you have to choose between 1/125 and 1/60 as these are the full stop increments we are using in this class.
How to Use the Sunny 16 for Better Control of your Exposures #
- First, Set your ISO to 100:
- Next, set your camera to Manual Mode:
- Then, set your camera to:
1/125 @ F16
Continuing on this control, if your ISO is set to 200 then in bright sun your exposure would be:
ISO 200, 1/250 @ f/16
What would your exposure be if your ISO was set to 400? (Remember, we are using the full stop range listed above, not all the numbers listed in your camera.) Did you come up with ISO 400, 1/500 @ f/16? If yes, then give yourself a pat on the back. You are well on your way.
