Understanding Digital Camera Exposure, Shutter Speed, f-stops

Camera Exposure Guide

Proper exposure is the holy Grail of all photography. Without the correct balance of the three elements shown on the triangle below the final image will be less than expected. What makes camera exposure more challenging is the fact that there is no one exposure combination that is always correct. Each scene that you are photographing, may require a different combination of the various corners of the exposure triangle.

Regardless of whether you paid $99 or $4,000 for your digital camera you your photography will look its best when you have the proper exposure. Proper exposure is a combination of the length of time the camera shutter and the amount of light received by the sensor. Exposure time is controlled by shutter speed and the light level is controlled by the lens aperture at a given ISO setting.

Proper use ISO sensitivity, shutter speed and lens aperture will assure that the image recorded by your camera is of the highest quality that your camera can capture.

Regardless of what you spent for your camera, a proper exposure will give you the best image from that camera. A good example of this is a well known picture of the plane that landed in the Hudson, that picture was taken by a cell phone camera.

Modern Digital cameras have amazing electronics and abilities to thank for you. They are not foolproof, knowing how to use the camera will guarantee you will have more fun with your photography.

iso The ISO setting is a number value for the digital cameras sensitivity to light. The higher the ISO numeric value the greater the sensitivity to light. in the past. When you purchased film you would be purchasing a certain ASA ASA is generally an obsolete term in today's photography environment ASA stood for American standards Association. While ISO stands for international standards organization.

Seasoned photographers often use the two terms interchangeably. Particularly if they've been shooting for a few years.

Generally speaking, you will want to use the lowest ISO that you can. The reason for this is that the higher the ISO number, the greater the chance you will have what is called digital grain or noise in your final image.

Camera Shutter Speed The shutter speed is the length of time the shutter is open. The shorter the duration the less light that it allows to reach the sensor. Shutter Speed is expressed in seconds(1", 2") or fractions of second (1/2, 1/80, 1/500, 1/2000)

The primary purpose of the shutter speed to freeze action. The higher the shutter speed the greater the action stopping ability while the lower the number the more light that is allowed into the camera.

If you are using a camera mode where the camera picks the shutter speed. You will want to be aware of the shutter speed is picking. Many cameras come with an 18 to 55 zoom lens. When picking a shutter speed for this type of lens. You would probably want to pick a shutter speed in the 50 to 60th of a second range. if you are using a telephoto setting the minimum shutter speed should often be equal to the focal length of the lens. For example, if you are using a 72-200 zoom. You should strive for a shutter speed of 200th of a second.

Unfortunately it is not always that straightforward. For example, if you are using a 70-200 mm lens and photographing a racecar, you will want a higher shutter speed.

Camera Aperture The APERTURE or F/Stop refers to the opening in the lens which controls the amount of light that passes through the lens and onto the camera sensor. The f-stop is the numeric representation of a mathematical formula for the width of the opening in the aperture to the distance to the image sensor. sometimes photographers will use the two terms interchangeably.

While the shutter speed controls how long the shutter is open and gives the ability to freeze action. The f-stop controls the amount of light coming through the lens and the amount of the image that is in focus. This is called the depth of field.

Light Meter Camera Exposure display. The graphic at the left is very similar to a display on your camera. when you look at your camera display, or through the viewfinder, you'll see a display similar to the graphic at the left, as well as other vital information about the exposure for that image. This information can include the shutter speed, the f-stop, the ISO, as well as other information. The actual settings will vary based upon your picture camera and options that you have selected. Many photographers will turn off all the display information on the back of the camera. A strict reliance on the LCD photo display on the back of a camera is not an accurate way to determine that you have the correct exposure.

Based upon the type seen that you are photographing each of the three corners of the triangle will have a different level of importance. you will want more shutter speed. If you're using a long lens, or there is a lot of movement. If you want more area in focus you want a higher f-stop number, which means that you may have to increase ISO or decrease shutter speed.

When your exposure is wrong you lose quality in your final picture.

When is comes to exposure film was a lot more forgiving than digital. Film could handle a wrong exposure more readily than digital. If you regularly shot with negative film you may have learned that over exposure was a safe rule while slide shooters learned that their film could handle under exposure better. Digital is much more like shooting slide film than negative film.

Look at the images below. Notice that at 3 steps over exposure there is still a visible image while at two steps over exposure the image is not viewable.

Correctly Exposed

Under 1 Step

Under 2 Steps

ISO 320 * f/5.6 * 1/250

ISO 320 * f/5.6 * 1/500

ISO 320 * f/5.6 * 1/1000

Under 3 Steps

Over 1 Step

Over 2 Step2

ISO 320 * f/5.6 * 1/2000

ISO 320 * f/5.6 * 1/125

ISO 320 * f/5.6 * 1/60

One of the concepts that many people do not understand is how the three corners of the triangle relate to each other. from an educational viewpoint, this has got to be one of the hardest things to teach.

Changing the shutter speed.
Shutter Speed Adjustments	ISO	F-Stop	Impact on Photo
125	100	8
250	100	5.6	Less depth of field. Better able to freeze action
500	100	4	Even less depth of field. Better able to freeze action

Changing the ISO
Shutter Speed	ISO - Adjustments	F-Stop
125	100	8
125	200	11	More depth of field.
125	400	16	Even more depth of field.

Changing the Shutter Speed
Shutter Speed	ISO	F-Stop - Adjustments
500	500	4
250	500	5.6	Less able to freeze action.
125	500	8	Less able to freeze action.

Developing an understanding of how the three corners of the triangle relate to each other can be difficult. As you try new things. Note your various camera settings both automatic and manual and see what works. As always, you need to visualize what you want your final image to look like.

What many of you just want to be able to take better pictures of your dog's kids flowers and the other things that your passion about in life. You'll still want to learn how to better visualize your photos before you take them and how to get the camera to work the way you want it to. Not the way it wants to work.

When your exposure is wrong you lose quality in your final picture.

Changing the shutter speed.

Changing the ISO