It's a fact that the interplay of F Stop, Shutter Speed, and Focal length of your lens is crucial to the final photographic image you create. Yet, it is surprising to find out how few photographers really understand the interaction among these three factors.

Before we discuss how the parts fit together, we will first describe each separate factor.

F Stops

Although you might have heard rumors to the contrary, the origin of the term F Stop is based on the initial of the inventor.

How much light comes through the lens is determined by the F stop setting, which refers to the degree of opening of the lens diaphragm.

Shutter speed

When we had film cameras, we had various forms of shutters that opened and closed and while also allowing light to "hit" the film, and could and still are used to control light, primarily, the Shutter Speed controls length of time the light will effect the film, or now "Digital Image Capture" device.

ISO

With both film and digital cameras, a standard was needed to specify how much or how little light is necessary to create an image on the film or the Digital Image Capture device. With film, the term was ASA, and recently the standard used is ISO.

Even though we don't use film anymore, we do have the ability to set a "film speed" in our new digital cameras. My understanding of the particulars is that it is actually an electronic change to the DCD (my own term, there are CCD's and other chips, but for this article their names are not important)

What does matter is that we can use the ISO to control our cameras to achieve a desired result we will discuss further in this article.

Focal length of Lenses

Now we get to the good stuff. We will demonstrate how all these elements work together to achieve results that you want depending upon the particular assignment.

EXAMPLE 1

Outdoors with bright sun.

We want to use a long, telephoto lens to capture a subject far away.

No tripod, hand hold the camera.

Even though our camera lens has a stabilizer feature, it's not 100% effective, so we will need a fast shutter speed to prevent "shake".

Setting ISO to 400 will usually allow Shutter Speed of 500-1000 with F Stop at F11 to F15.

Next, we'll take up an example that may be more of a challenge.

Example 2

Outside location, not bright.

Again we want to use a long, telephoto lens to capture the distant subject.

No tripod. Hand held camera.

Since we can't depend on the stabilizer lens 100%, we need a fast shutter speed to prevent the camera shake effect in our image.

Here's where you need to understand the interplay of all the facts so you make the right choices-

a. you can increase your ISO which will allow you to maintain your shutter speed.

b. If you reduce your F Stop (open your lens), you will sacrifice the total of area in focus (Depth of Field).

Now we will sort out the relationships among these factors.

When you increase/decrease your F Stop one full stop- 5.6 to 8, or 2.8 to 4, reversed, these are full F Stops.

When you increase/decrease Shutter Speed, from 125th to 250th of a second, or 1000th to 2000th of a second, or reversed, are double, or if reversed, allow double the amount of light, or the amount of light that will effect your "film".

Result of increasing F Stop from f8 to f11 is "losing" one full stop of light.

When you increase shutter speed from 1/500th to 1/1000th, you "lose" one full stop of light.

If you "Double" your ISO from 400 to 800 or 800 to 1600, you gain one full "Stop" of light.

Notice that when working with ISO, F Stops, or Shutter Speeds, we refer to the changes in values at "Stops of Light".

Relationships Between Elements

You can use any and all of these elements to control your camera settings. F Stops control Depth of Field (amount of are in focus). Shutter Speeds control movement, or stop movement of action, or allow movement for effect. ISO controls amounts of light.

In Real Situations

Suppose you want to make your backgrounds out of focus. If you start out with your lens at F8 with a 250th of a second Shutter Speed, to make your background out of focus, reduce your Depth of Field by opening your lens to F4, while increasing your shutter speed to one 100th of a second.

Here you opened your lens 2 "Stops". The change in your Shutter Speed from 250 to 1000, in effect doubled from 250 to 500, and then doubled again from 500 to 1000.

If in the above scenario you were using an ISO of 800, you could reduce the ISO to 400, thus reducing the light by which would allow you to only increase your shutter speed once (double), from 250 to 500.

If you are using your camera on the automated "Program" setting, you are not taking full advantage of the adjustable controls of F Stop, ISO, and Shutter Speed that you can combine to unleash your creativity.

Learn what these settings can do for you and your "creative world" will explode.

Though some "Photojournalistic" style photographers have at times thought I was criticizing their entire body of work, they misunderstand my viewpoint. I want them to realize that by incorporating the basic technical skills in their work, their work will jump to new heights of creativity.

So many eager individuals, with a love of photography and some small successes, decide to jump into the business of Professional Photographer, before they know the basics of what it takes to create the beautiful pictures that become treasured records of their clients' life events.

Would you go to a Doctor whose credentials consist of letters of testimony from their friends and family that they always wanted to be a Doctor, and they seem to have natural abilities to help people? I think not. As a Professional Photographer you will serve your clients best by preparing and learning so that you provide expert service. Without basic skills, you may be doing the best you can, but is it good enough to be called a Professional?

Next chapter- How all of this works with your electronic flash