Exposure

Lesson 1: Exposure

In the previous lessons, you have researched a great deal, sifted through the information, chosen your camera and equipment, and learned how to maneuver through the different settings in your camera. Now, it is time to take this learning a step further and understand the basics of photography. In the following lessons, you will be able to understand the theory of photography and put it into practice.

What is Exposure in Photography?

Exposure is the amount of light that reaches the sensor of your camera. It determines how light or dark your photograph will be. There are three settings that affect exposure.

• Shutter speed
• ISO
• Aperture

Each of these have an effect on one another, ultimately giving you your exposure for your camera to take the photograph.

We discussed before about using Av mode or Aperture Priority mode. In this mode, you have the ability to choose your aperture and ISO. When these are set, you can focus on your subject and take the photo. The camera automatically calculates the shutter speed giving you your exposure.

In our second discussed mode, M or Manual Mode, you have the ability to choose your shutter speed, ISO, and aperture. We will discuss these aspects of photography in detail here, explain how they affect one another, and how to use them in photography.

ISO

International Standards Organization, or ISO, governs the sensitivity standards in cameras. The number associated with your ISO determines how sensitive your camera is to light, with the lower being less sensitive and higher being more sensitive.

On your camera, your ISO ranges from 100 to 12,800. Sometimes these numbers can be lower or even higher depending on the camera. So, what do you do with ISO? How does it affect your photo? When do you change the ISO value?

How does ISO affect exposure?

As we said, the lower the number then the less sensitive the sensor is to light. If your sensor is less sensitive to light, you need a longer shutter speed to compensate. Therefore, the higher the ISO, the more sensitive to light, and a shorter shutter speed is the result.

When do you change the ISO value?

Generally you want to keep your ISO as low as possible. I have my ISO value set at 100 by default. Depending on the scene and subject you are shooting, you will have to adjust your ISO. For example, if you are shooting a scene in bright daylight, you will not need to change your ISO setting. However, if you are photographing in the early morning or afternoon, then you will need to adjust your ISO setting. Additionally, if you are photographing at night, then your ISO value will need to be much higher. The higher the number, the more noise will enter your photograph.

For example, in this low light situation I was forced to use my camera in my hand and turn my ISO up to 1600. Even still, the result was a blurry due to the long shutter speed and grainy due to the high ISO value.

Noise is visual distortion within photography. This can be seen as grain or even discoloration in your photograph. There is an easy way to avoid this. Keep your ISO setting as low as possible. Therefore, to avoid noise and motion blur in low light situations, you will need to use a tripod or somewhere to hold your camera. The low ISO will force your camera to use a longer shutter speed, and if you are using your camera in your hand, your photo will be blurry.

In this photo, I needed to use an ISO of 1600 to have a shorter shutter speed of 1/125 of a second while shooting with the camera in my hand. The result was an extremely grainy photograph. I then changed the photo to monochrome to create a vintage look with the grainy shot.

In conclusion, always use the lowest ISO possible. If you are shooting in a low light situation while the camera is in your hand, you will need to use a higher ISO value to reduce the shutter speed. Otherwise, your photo will be blurry. Alternatively, use a tripod to allow you to keep your camera stable while it takes the photo.

Aperture

Inside of your lens is a diaphragm that is able to open and close to allow light to pass through. This controls the depth of field, or what appears to be in focus within the photograph. Much like ISO, the more light allowed through your lens, the shorter the shutter speed will be.

Aperture is displayed as a value of f/2 to f/22 (just an example of a range of values, all lenses differ in their aperture values). The smaller the aperture value, the larger the diaphragm is opening and allowing more light in. Alternatively, the larger the value, the smaller the diaphragm is opening and allowing less light in.

When to Adjust the Aperture Value?

Aperture directly affects the depth of field, or what is in focus in your photograph. Therefore, if you want to achieve a shallow depth of field, you will want to use a small aperture value allowing more light to pass through the lens. The shallow depth of field keeps only the subject you choose to focus on in your frame in focus. The remaining scene is blurry, whether it is in the foreground or background. This is good for portrait shots or when you want to shorten the shutter speed.

As you can see in the photo, I used an aperture value of f/5.6 and focused on the pineapple. This resulted in a blurry background.

If you want to achieve a large depth of field, you will use a bigger aperture value allowing less light to pass through. The large depth of field keeps everything in your frame in focus, from the foreground to the background. This is good for landscape shots, but more difficult when the scene you are shooting is not well lit.

In this photo, I used an aperture value of f/18 which resulted in everything to be in focus in the photograph.

In conclusion, aperture directly affects the depth of field. A low value opens the diaphragm in the lens to allow more light onto the sensor. It creates the blurry effect within photographs and is good for portraits or low light situations to reduce the shutter speed. A high value closes the diaphragm, reducing the amount of light that reaches the sensor. This keeps everything in the frame in focus, from foreground to background, and is useful for landscape photography.

Shutter Speed

Shutter speed is affected by aperture and ISO directly. It is the amount of time that the shutter is open, allowing light to reach the sensor. When there is a lack of light, the shutter will need to stay open longer for enough light to reach it to capture the photograph. Alternatively, when there is an abundance of light, the shutter will stay open for a shorter amount of time.

When the aperture is smaller (the f/value is a bigger number and the depth of field is larger keeping most of the scene in focus), this also requires the shutter to remain open longer. In addition, if the ISO is lower in value, then the shutter will need to stay open longer. This is called the exposure triangle.

Aperture, ISO, and shutter speed give you your exposure. If you want a longer exposure, simply set your aperture to a high value, your ISO to a low value, thus lengthening the shutter speed. This is good for scenes with low lighting that you are able to capture during a long period of time like stars. Alternatively, if you want to capture a fast-moving subject, you will need a shorter exposure. Simply set your aperture to a low value, your ISO higher (keeping in mind the higher you go, then the lower your image quality will be), thus shortening the shutter speed.

This photo was taken with a 30 second shutter speed.

This photo took 60 second shutter speed to capture the light from the stars and foreground scenery.