Basic Photography: Camera Settings
Apertures? ISOs? F-stops? What the...?
Thank goodness for our cameras' "Auto" settings. With them, the camera will adjust its own settings in the way that it thinks will make for the best picture. Usually, it is very good at what it does. It's kind of amazing, really.
However, sometimes the Auto setting doesn't take quite the photo you were hoping for and you will want to tweak your pictures. Then you will need to know what these terms mean. But don't worry—it's easier than you think.
Note: this lesson makes extensive use of the Photonhead.com website. If you are interested in photography, I recommend exploring their whole site—it's a fantastic resource.
Your Assignment
Read through the lesson below. As you move through the lesson, you will come across different Tasks. Complete each task as directed, either writing your answers on a sheet of paper or typing them in Word.
Using Stops
The word photography comes from Greek, and means "light writing." When you take a photo, you are creating a picture out of pure light. Obviously, then, how much light you use is going to have a big effect on your picture. You can control how much light you use by working with stops.
A stop is a general term for a one-level change in the amount of light. Stops are relative. Moving up one stop doubles the amount of light the camera lets in; moving down one stop cuts it in half.
There are three settings on a digital camera that affect the amount of light being used: shutter speed, aperture, and film speed. Each one has a different numbering system, but all of them are divided into stops. A change in one level on any one of the three is a change of one stop.
When it comes to changing the amount of light being let into the camera, a change of one stop in any of the three settings would have the same effect. However, the picture will come out slightly differently, as you will see.
Furthermore, if you want to keep the same amount of light, but want to change one setting, you can accomplish that by changing that setting, and then moving another setting in the other direction. For example, if you want to move the shutter speed up two stops, you could move aperture or film speed down two stops, or you could move each of them down one stop for a total of two between them.
Task
Go to the Stops article at Photonhead. Scroll to the middle of the page, under the "Stops Are Interchangable" heading. You will see a box with listings of possible settings for shutter speed, aperture, and film speed. It is currently set to a shutter speed of 1/125 of one second, an aperture of f5.6, and a film speed of ISO100.
Notice the green marker beneath the settings, showing the level of exposure (the amount of light your picture is being "exposed" to). Experiment with changing the settings, trying to keep the green marker in the middle so the exposure stays the same. They key is, for every stop you increase on one setting, you have to decrease one stop on another.
On your answer sheet, write three headings: Shutter Speed, Aperture, and Film Speed. Then answer the following:
1 & 2: Set the shutter speed to 1/30 sec. On your answer sheet, list two possible combinations of settings that would both maintain the original exposure.
3 & 4: Set the aperture to f11. List two possible combinations of settings that would maintain the original exposure.
5 & 6: Set the film speed to ISO400. List two possible combinations that would maintain the original exposure.
Shutter and Aperture
Usually, you will only change film speed as a last resort (you'll learn why below). That means that you will mostly be concerned with shutter speed and aperture.
The shutter of the camera is a door that opens to let light in, like the shutters on the window of a house. The longer it is open, the more light it lets in. Shutter speed is measured in fractions of a second. If you are in a location with low light, like when you are indoors, you could use a slow shutter speed to leave the shutter open longer and let in more light (see the Jewel of the Sea in Figure 1). However, this causes a problem if there is anything moving in the picture. A longer exposure of a subject in motion will be blurry. Sometimes you may choose to do this on purpose (see the Athens Supercross in Figure 1), but usually it's not desirable.
| Figure 1: Shutter Speed | |
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Interior of The Jewel of the Seas |
The Athens Supercross. Sometimes a blurry effect is |
The aperture of the camera refers to the size of the hole through which light can enter the camera. The main effect of a change in aperture is depth of field, or how deep or shallow your picture appears.
Try this experiment. Make a circle with your thumb and index finger. Look in the distance for something that appears slightly out of focus to you. Look at it through the circle you made with your thumb and finger. Notice how it appears sharper? The circle is a smaller aperture, and it creates a longer depth of field, bringing the distant object into better focus. Cool, huh?
Aperture is measured in f-stops. The higher the number, the more light is kept out—In other words, the smaller the hole. The smaller the hole, the further away objects appear in focus, which makes the picture look deeper.
Photographers often use a shallow depth of field when photographing people, to throw the background slightly out of focus (see the girl on the left in Figure 2). A greater depth of field captures details further away (see the train track in Figure 2).
| Figure 2: Aperture | |
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Tired after a long day of swimming. A shallow depth of |
Train tracks. A longer depth of field |
Task
Go to the Shutter and Aperture SimCam at Photonhead. Follow the directions in the SimCam box. On your answer sheet, answer the following:
- Describe both of the photos you "took."
- How are they the same?
- How are they different?
- How are these similarities and differences explained by shutter speed and aperture?
Film Speed
Under some conditions, the only way you can get enough exposure may be to change your film speed. If you are using a film camera, the only way to change your film speed is to change your film. On a digital camera, however, you can just change the camera settings.
You may see film measured in units of either ASA or ISO. For our purposes here, they are the same thing. The lower the number, the "slower" the film is said to be. Faster film has a higher number.
Slower film is less sensitive to light, so it requires a lot of light to get a good image. Each step up in film speed is a reduction of the equivalent of one stop. Slower film also takes the crispest pictures. For that reason, you want to use the slowest film you can that will still produce a good image in the light that you have.
Task
Go to the Film Speed SimCam at Photonhead. Follow the directions. On your answer sheet:
- Explain why in the original images, the picture taken with 400ASA film is so much brighter.
- Explain how changing the aperture or shutter speed compensates for this difference.
- Set the shutter speed to 1/125 sec. What aperture setting must you use to get the same result?
- Get the 400ASA photo to match, as closely as possible, the 100ASA picture. Compare the clarity of the two pictures.
- Why is there a difference in clarity?
- If you need to increase exposure, why should you only increase film speed as a last resort?
Camera Shake
If you move the camera while the shutter is open, the image will be blurry. If you're using a fast shutter speed, this probably won't be a problem because you wont have time to move the camera. Slower speeds are a different story. The absolute slowest shutter speed most people can use while holding a camera in their hands without having the image get blurry is about 1/60 sec.
Professional photographers avoid camera shake by doing the following two things whenever possible:
- Using a tripod, because it is perfectly still, unlike your hands.
- Using a cable release or the auto timer function on the camera, because the motion of pushing the shutter button on the camera may be enough to move it.
Photo shake is a bigger problem when zooming in on something with a telephoto lens.
Task
Go to the Camera Shake SimCam at Photonhead. Experiment with the settings on the zoom picture. On your answer sheet, answer the following:
- What combination of aperture and shutter speed settings gives you the sharpest focus on the man?
- What happens to the background of the photo at this setting?
- Why does the background look this way?
Note on Photos Used in This Lesson
All photos used in this lesson were downloaded from stock.xchg and are used in accordance with their usage policies. This site is a great resource for stock photos of all kinds of things.