Basic Exposure

This month I am pausing my writing on Lightroom and starting a series on Beginning Photography. In September, I will teach a workshop for beginners.

This first article is on exposure. Exposure is one of the most important elements of photography and understanding how good exposure is accomplished will increase the quality of your images.

Exposure = ISO + Shutter + Aperture.


Exposure is a combination of three attributes that the camera can record. ISO, Shutter Speed, and Aperture. Using the three attributes correctly will give you a technically or accurate exposure in your image.


This is the sensitively of the sensor of your camera to record or capture the light hitting the sensor during an exposure. ISO has a measuring standard or scale and measures intensity. Typical on a camera is a value of ISO 100. It is not important to know how much light gets recorded but to understand what the camera is doing. If you change the camera by one stop up to ISO 200. A “stop up” is the doubling the value and a “stop down” is halving the value. When the ISO changed from 100 to 200 or one stop, the sensor can record twice as much light. If the ISO change one more “stop up” it would be ISO 400 or doubling again. A typical measurement of stops could be ISO 100, 200, 400, 800, 1600, 3200, and higher. You see how a stop is up by doubling. It also moves down. If your camera was set to 800 ISO because the scene was overcast and now the sun is out, you may might a determination to lower the ISO from 800 to 100 which if counted out as three stops. 800 went to 400 (one stop), 400 to 200 (one stop), 200 to 100 (one stop). Counting the one stops is summed up as three stops.

Why are we allow to change the sensitively? Sometimes, we need to shoot at dusk or indoors other times it may be a bright sunny day.

When the ISO increases an attribute that is introduced is “noise” (looks grainy). This may or may not be acceptable. Also, the effective range or dynamic range (light to dark values) decreases.

Shutter Speed

The shutter is often a mechanical device in your camera, it opens and closes. Like a curtain in your living room, open it to allow in light, or a closed curtain does not allow light in. A shutter opens and closes on time. A short amount of time, such as 1/60 of a second. When you push the shutter, and hear the camera pop or click, that is the shutter opening and closing. A typical scale of a shutter in full stops.

Lower values, 1”, ½,” ¼,” ⅛,” 1/16,” 1/30,” 1/60,” 1/125,” 1/250,” 1/500,” 1/1000” or higher values

The attributes of the shutter are to freeze motion or allow blur. The higher shutter speed value would freeze motion, lower values like 3” would blur moving water. It is hard if not impossible to handhold a camera below 1/60” so tripods are used to stabilize the camera.


The aperture is often in the lens of the camera. The human eye has a similar mechanism, the iris. It opens (dilates) to brightness or darkness. Example, if may take a moment for your eye to adjust when entering a theater.

The Aperture has a scale as well. Of all the scales, this one is odd, and in time you will memorize it. Scale values such as f1.4, f1.8, f2.0, f2.8, f4.0, f5.6, f8, f11, f16, f22, f32 and higher.

The attributes of aperture change the focal distance. There is one point where the lens creates an absolute focus, then in front of and behind that point begins to go out of focus. The smaller the Aperture opening in the lens (BTW, it is a bigger number) such as F22, will produce more acceptable focus than an F4.

We use aperture to isolate a subject features, such as portraiture. You may want the background to be blurred, so your subject has the focus and holds interest to the person viewing the image.



Camera Controls

Most cameras and phones today have the ability for the image maker to control these attributes. Often the photographer has to make choices. Choices such as the light may be little or intense, the action needs to be frozen or blurred, or the focus is isolated, or everything in the image should be in focus. Such as a landscape should have the foreground, middleground, and background in focus.

Each image requires a choice. You can shoot in manual mode where you control all three attributes, or just aperture and shutter. Use “modes” on your camera to pick shutter or aperture priority. Example, when I shoot street photography, I want control over the focal plane, so I shot in aperture priority, which controls what is in focus on my subject. I choose a small number like f4 for a single person, and f8 for a small group.  I choose the aperture, and the camera controls the shutter, so I can be quick in getting an image. I use an ISO which is based on my available light.

Shutter priority is often displayed on the mode dial as an S or Tv on the dial or aperture is an A or Av.


The mode dial has other settings to help you make better images. The icons are for action (running man), landscape (boxed mountain), macro (flower), portrait (profile of a person), Shown in my example in a counterclockwise direction. Your camera may have more or fewer options, and the icons may be different but will be similar.

Since you committed a financial investment today and it is all up front (film days, you needed to buy and process your images), you can shoot images today at close to no cost (except time) to learn the exposure attributes work. Turn the mode dial, like on S and shoot away. If the images are unacceptable, they can be thrown out. Practice and learn to control your exposure. By bold and shoot in manual mode M and learn what not to do, but once mastering it, it will be the preferred method for many outings.