Do You Know How F Stops, Shutter Speeds, And Iso Are Related?

F Stops, Shutter Speeds and ISO- How do they relate?

When you think that the relationship between your F Stop and Shutter Speed, Focal length of your lens, and your ISO can make such a difference in the final image you create, it is surprising how few photographers actually understand the intricate relationships between them.

First we will define each factor, followed by details of how each factor affects the others.

F STOPS

No, that name is not derived from a vulgar term. The concept of F stops was invented by a man whose initial was F.

They are the diaphragm, or the opening of the lens. The F Stop determines the amount of light that will pass through the lens.

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 film, we needed a standard to determine how much or little light was required to create an image on the film. As films were developed with varying "speeds", or ability to capture more or less light, a standard was needed. Originally it was called ASA, for American Standards Association. About 5 years ago the new term ISO became popular. International Standards Association.

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)

Now that you know that the ISO setting in your digital camera compares to the film speed setting in a film camera, we will describe the details of the effect that you can achieve with the ISO setting later 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 One

Location: outside, bright sun

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

Camera to be hand held, not using a tripod.

Since we cannot depend totally on stabilizer lenses, we will need to use a fast shutter speed to keep the camera shake from affecting our picture.

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

In this next example, you might have problems taking pictures of your subject.

Example Two

Outside location, not bright.

Our subject is still at a distance, and we want to use a long, telephoto lens to capture the shot.

We will hand hold the camera. No tripod.

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.

Now you have to make choices-

a. if you want to maintain your shutter speed, you could increase the ISO.

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

Let's explain relationships between all of these elements.

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.

If you increase shutter speed from 1/125 of a second, to 1/250th of a second, or from 1/1000th of a second to 1/2000th of a second, you reduce the amount of light to your film or chip by one half, and if you decrease shutter speed from 1/250 second to 1/125 second, or 1/2000 second to 1/1000 second, you double the amount of light getting to the film or chip.

Equation: If you increase your F Stop from F8 to F11 you "Lose" one full stop of light.

Increasing shutter speed from 1/500 to 1/1000th of a second results in "losing" one full stop of light.

To gain one full stop of light, double your ISO, such as from 400 to 800, or 800 to 1600.

Important note: "Stops of Light" is the terminology we use whether we are discussing the effects of working with ISO, F Stops, or Shutter Speeds.

Relationships Between Elements

Any or all of these factors can be used to control your camera settings. Use F Stop to control Depth of Field (area that is in focus). Use Shutter Speeds to control movement, or stop movement, or allow movement to create special effects. Use ISO to control amount 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 want to discover the extent of your creativity with your camera, get away from taking pictures with your camera set on "Program," and really USE the capabilities of your "fully adjustable camera".

You'll open new worlds of creativity by learning to manipulate these settings.

There are some in the photographic community who believed I was generally criticizing the "Photojournalistic Style" of photographers. However, that has not been my point. The basis of my criticism of the photojournalistic genre was that those who pursue that style, without learning the basic technical elements presented here, are shortchanging themselves and their customers. With the basics down pat, their pictures can be ever more beautiful and intriguing.

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.

Simply being told by friend and relatives that they "have a good eye", is simply not enough. There is not question, they achieve images, but are they achieving the best image they can achieve? When we get our haircut, or our visit our Dentist to remedy a painful toothache, we expect these people to do the best they are capable of, not just what they can get away with.

How the elements discussed here work with your electronic flash will be in our next article.

source: http://contentdig.com/

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