LA 09 – Exposure Basics

From the time digital cameras (SLR = Single-Lens Reflex cameras) arrived the photography scene, it has been a lot easier to learn the art of photography and take good pictures. This has to do with the fast accessibility to the pictures and the understanding of the connection between light exposure and camera settings. None or the less, you have to now the basics of how your camera works. I’m working with my Canon EOS 500D SLR camera with the kit EF-S 18-55mm f/3.5-5.6 IS lens.

Question 1 – Observation and analysis

1) Name all the functions/ buttons on the front of your camera

2) Name all the functions/ buttons on the back of your camera

The top of the camera looks like this:

Canon EOS 500D Camera Top

Exposure

Exposure is the process whereby the light reflecting off a subject reflects through an opening in the camera lens for a defined period of time onto the camera sensor. The combination of the lens opening, shutter speed and sensor sensitivity is used to achieve propper exposure value (EV) for the scene. The EV is the sum of these components necessary to properly expose a scene. A relationship exists between these factors that is sometimes referred to as the «Exposure Triangle».

At each point of the triangle lies one of the factors of exposure:

  • ISO: Determines the sensitivity of the camera sensor. ISO stands for the International Organization of Standardization, but the acronym is used as a term to describe the sensitivity of the camera sensor to light. The higher the sensitivity, the less light is required for a good exposure. These values are carryover from the days of traditional colour and black white films.
  • Aperture: Also referred to as the f-stop, this determines how much light passes through the lens at once.
  • Shutter speed: Controls the length of time that light is allowed to hit the sensor.

A change to any of these factors requires changing one or more of the other two (reciprocal change).

 

3) Explain how you would set the correct ISO

To determine the correct ISO,

  1. Activate the camera by lightly pressing the shutter release button.
  2. Press the ISO button on the top of the camera
  3. Use the Main dial to select an IOS between 100 and 6400.
  4. Lightly press the shutter release button or press ISO button again to lock in your change.

You can also change the ISO without taking your eye from the viewfinder by following the same steps as above. When you press the ISO button, you will see all of the camera settings in the viewfinder disappear, leaving just ISO information viewable. Once you press Set button, your new ISO setting will be displayed along with the regular shooting-data. This will get easier to do as you become more familiar with the camera buttons.

 

4) Explain how you would change the aperture

The lens aperture will vary a bit depending on which lens I am using, because different lenses have different maximum apertures.

There are different ways of change the aperture depending on which mode the camera is in. In the Program mode (P on the Mode Dial), I would turn the Main dial counterclockwise to get smaller aperture (to for example get a narrow depth of field). The camera shifts the shutter speed and aperture accordingly in order to get a proper exposure.

In the Aperture Value Mode (AV), commonly known as Aperture Priority Mode, I would first set the ISO and then I can change the shutter speed. I would point at my subject and then activate the camera meter by depressing the shutter button halfway. Now I would view the exposure information in the bottom area of the viewfinder or by looking at the rear LCD panel. While the meter is activated, I will use my index finger to roll the Main dial left and right to see the change exposure values. Rolling the dial to the right for a smaller aperture (higher f-stop number) and to the left for a larger aperture (smaller f-stop number).

In the Manual Mode (M) I would repeat the same process, and to set my exposure using aperture, I would depress the shutter button until the meter is activated. Then, using my thumb, I will hold in on the AV button and then use my index finger to turn the Main dial, right for a smaller aperture (large f-stop number) and left for a larger aperture (small f-stop number).

 

5) Explain how you would change the shutter speed

The speeds on my camera range from as long as 30 seconds to as short as 1/4000 of a second. Which speed to select, depends on the circumstances and the effect that I want to achieve. In Program Mode, I would rotate the Main dial clockwise to get faster shutter speed (for example to stop the action in a picture). The camera shifts the shutter speed and aperture accordingly in order to get a proper exposure.

In the Time Value Mode (TV), also referred to as the Shutter priority Mode, I would first set the ISO and then I can change the shutter speed. I would point at my subject and then activate the camera meter by depressing the shutter button halfway. Now I would view the exposure information in the bottom area of the viewfinder or by looking at the rear LCD panel. While the meter is activated, I will use my index finger to roll the Main dial left and right to see the change exposure values. Rolling the dial to the right for faster shutter speed and to the left for slower speed.

In the Manual Mode (M) I would repeat the same process, but while the meter is activated, I would use my index finger to roll the Main dial left and right to change the shutter speed value until the exposure mark is lined up with the zero mark. the exposure information is displayed by a scale with marks from that run from -2 to +2 stops. A proper exposure will line up with the arrow mark in the middle.

 

Resources

Lesson
«Know Your Camera» from Noroff School
Lynda course «Introduction to Photography» with Ben Long

Litterature
«Canon Rebel T1i/500D – From Snapshots to Great Shots», chapter 1 (page 1 – 23) and chapter 2 (page 24 – 55), by Jeff Revel. I have also looked into chapter 3 and 4 to find the information needed.

Websites
https://www.canon.no/support/consumer_products/products/cameras/digital_slr/eos_500d.aspx?type=drivers&language=&os=macOS%2010.14%20(Mojave)

http://files.canon-europe.com/files/soft33601/Manual/EOS500D_EN_Flat.pdf

 


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