Photography tips articles and definitions

The Dual Effects of Camera Settings

I have described to you 3 settings on your camera that you can manipulate and I have also described their major functions; the aperture determines how much light passes through the lens, the shutter determines how long that light is passing to the film/sensor and the ISO determines how sensitive the film/sensor is to the light passing through the lens.  But how do we decide which settings to tug and pull on to obtain that magic amount of light? The simple answer is: It depends

Aperture and Depth of Field

The aperture serves two main purposes. The first is how much light comes through but the second is that it determines your depth of field.  Depth of field (DOF) is the amount of in-focus area in your image.

You may be wondering how depth of field is obtained.  It is a combination of three things you can control. The depth of field is determined by aperture setting, focal length, and focal distance (the size of your film or sensor also plays a part). All else being equal: large apertures will yield a smaller depth of field than small ones; longer focal lengths will yield a smaller depth of field than shorter ones and closer focal distances will yield a smaller depth of field than further ones.

What you set your aperture to is going to depend on what you are trying to achieve with your photograph. As seen in the images below, by varying the depth of field you can alter the look and feel of a photograph pretty dramatically.

Note how it appears that everything is in focus. The depth of field in this image is enormous. From the bottom of the frame (just in front of my feet as I took this photo) to the middle of the frame (trees 180 yards away), everything remains in focus. This was the intent as I wanted the viewer to see the entire scene. Please note that this was taken with a wide angle lens with a very small aperture setting.

For this image, I utilized a narrow depth of field. My goal here was for the viewer to feel close to the subject and more involved with the scene. The narrow depth of field was created here by the closeness of the camera to the subject but also the use of a large aperture.

Shutter Speed

Shutter speed determines how much time the film or sensor is exposed to light.  Unlike ISO, however, there are many times that adjusting your shutter speed is going to actually change the photograph in a meaningful way. 

I find this to be one of the hardest constructs in photography to initially grasp but it is also one of the most important. Changing the shutter speed determines how sharp the content in your image is going to be. Please note this not to be confused with focus.  When you look at a stationary object, it does not move and because of this it appears "sharp" to us.

Photography literally means painting with light and if you think of the film or sensor in your camera as a canvas it helps to understand how shutter speed affects the crispness of your image.  Your lens captures a scene and then paints that scene by projecting it onto the film/sensor, much like a projector in a classroom does.  Wh Photography literally means painting with light and if you think of the film or sensor in your camera as a canvas it helps to understand how shutter speed affects the crispness of your image.  Your lens captures a scene and then paints that scene onto a light by projecting it onto the film/sensor, much like a projector in a classroom does.  If there is movement of the object or the canvas while that painting is being painted, then the image begins to blur. 

In this image I wanted to capture the action as crisply as possible. This required a higher ISO and a larger aperture setting to allow for a shorter shutter speed.

Sometimes blurring the content of your image is desirable however. In this image, I was attempting to photograph the speed and power of the sprinter. The motion in the runners arms was captured by using a slower shutter speed. To achieve this in the bright sunlight, I had to decrease the ISO and make the aperture smaller.

ISO

Of the three settings, ISO is typically the easiest to set.  Unlike shutter speed or depth of field, the side effect to adjusting your ISO is rarely used to enhance an image (I say rarely because like any other setting, it depends on what you are trying to achieve). 

What does ISO do? The ISO determines the sensitivity to light, as we mentioned. But setting higher ISO’s will create grain or noise (essentially these two things are the same). The higher the ISO, the more “dirty” your image appears.  In general, you want to keep the ISO as low as possible as long as it allows you to maintain what you are trying to achieve with your shutter speed and aperture.

It is important to note that as digital technology improves, the amount of noise at a given ISO seems to be decreasing. Below are two examples of ISO 3200 images from two different cameras.

This image was taken at ISO 3200 by a Canon 1DmkII

This image was taken at ISO 3200 by a Canon 1DmkI