Your camera is a device that takes pictures, but there is a lot going on behind the scenes that the software in your camera takes care of in fractions of a second.

With your camera in an automatic or semi-automatic mode, as you press the shutter button half way down your camera does two operations; 1) focuses on the subject you are pointing at and 2) measures the exposure so the camera can set what it thinks are the correct aperture, shutter speed and ISO settings. Once you finish pressing the shutter button all the way down the camera captures the image. As you review the captured image you may notice that the result may not be quite what you expected, it may be too bright or too dark depending on the decision that the camera made based on the current lighting conditions, main subject, and surrounding area.

The camera software does not yet have the artificial intelligence to always determine the optimum settings to achieve a correct exposure for any given scene. This is where you, have the ability to control the camera to make the next image a bit brighter or darker depending on the “Exposure Compensation” setting.

In automatic, or semi-automatic modes you can force the camera’s light meter to a brighter or darker setting by changing the “Exposure Compensation”. “Exposure Compensation” is also referred to as “Exposure Value” or “EV” for short. The first time you set the EV away from the default setting of “0” and you want the next image to be brighter move the setting toward “+1”, or if you want the next image to be darker move the setting toward “-1”. Each mark on the meter is in 1/3 stop increments in which three movements equals a stop.

This tells the camera that what ever it thinks is the right exposure, you have chosen to make it brighter or darker depending on your EV setting. This is how you work collaboratively with the camera to create a proper exposure even though the camera is in an automatic or semi-automatic mode.

As an example lets see how to change the EV setting on two Cameras:

1. To change the EV setting on a Canon SX30 in aperture priority mode, “Av” (manual pg 73); press the “+/-” or up arrow button, on the back of the camera, until you see +/-0, then turn the “dial”, on the back of the camera, clockwise to make the EV brighter, positive direction, or counter clockwise to make it darker, negative direction.
2. To change the EV setting on a Canon T6i in aperture priority mode, “Av” (manual pg 159); press the “Av+/-” button, on the back of the camera, and then turn the “main dial”, on the top right of the camera, clockwise to make the EV brighter, positive direction, or counter clockwise to make it darker, negative direction.

As an exercise, use your camera to take three pictures of the same subject; image (1) with the EV set to “0”, image (2) with the EV set to “+1”, and image (3) with the EV set to “-1”. You will notice that the 2nd image is brightest, the 1st image is darker than image 2 and the 3rd image is the darkest.

There is an additional “metering mode” control that also helps the camera further understand what type of subject you are trying to take an image of, which will be discussed in our next lesson.

The exposure triangle is an analogy or standard way to explain the result that aperture, shutter speed, and ISO have on exposure. Each setting represents a side of the triangle with the overall size of the triangle representing the exposure (brightness) of the image.

You can think of the triangle as a piece of pie or a slice of pizza, the bigger the slice the brighter the photo. Make the photo brighter or darker by adjusting one or more of the three settings. The setting(s) you choose to change is based on the creative control that we have learned in our past lessons; Creative control with aperture, and “Motion” the creative control behind shutter speed.

If you slow down the shutter speed, toward 1/4, there is a longer duration for the light to be available to the sensor resulting in a brighter exposure and as a result a larger triangle. Conversely, if you speed up the shutter speed, toward 1/1000, there is a shorter duration resulting in a darker exposure.

By increasing the size of the aperture, toward f/2.8, which allows more light into the camera resulting in a brighter exposure. Conversely, decreasing the size, toward f/16, of the aperture reduces the light into the camera resulting in a darker exposure.

Also, increasing, toward 1600 (more noise), the ISO amplifies the image from the sensor resulting in a brighter exposure. Conversely, if we decrease, toward 100 (less noise), the ISO it decreases the amplification resulting in a darker exposure.

Adjusting any of the three settings; aperture, shutter speed, and/or ISO, requires consideration of the creative control that aperture and shutter speed provide as well as considering the quality of our image with ISO at the same time achieving a proper exposure.

In our next lesson we are going to discuss how the camera measures exposure and how you can help the camera control the exposure in auto and semi-automatic modes.