Matt Bango Photography

Aperture, shutter speed and ISO, the big 3 that usually cause the most confusion early on. If you can get a grasp on how the big 3 work together to affect your exposures, taking pictures will be a much more pleasant experience and will have a lot less frustration. Once you understand it, it is like riding a bike. It may take some time and effort to learn, but once you learn it you won’t forget it. The one that causes the most confusion out of the big 3 is usually aperture. Why? Well there’s that sequence of numbers that seem to work backwards and that little matter of depth of field. Understand the big 3 and the rest will come much, much easier. While this article is geared for SLR cameras, the concept still applies to point and shoot cameras.

So what is aperture exactly? Aperture can simply be put as an opening that regulates how much light is let through your lens, into your camera and onto the image sensor (digital) or film. All lenses have an opening (aperture) that regulates the amount of light that will pass through to the CCD or film. The light is regulated by a series of overlapping blades arranged in a circle inside the camera lens. The opening at the center of these blades is what the aperture actually is.

This is where a lot of people get confused. Aperture is measured in increments called f-stops. The smaller the f-stop number, the larger the aperture is open (meaning more light can come in). A f-stop of f/1.8 will let in a large amount of light as opposed to an f-stop of f/22 which decreases the amount of light let into the camera. This can easily be seen in the image below, showing the different sized openings at different f-stop numbers.

The range of the aperture is determined by the lens itself. You can see the f-stop numbers printed on the lens. For example, my Nikon 28-80mm lens has “F3.3 – 5.6″ printed on the lens. This means at 28mm the largest F-stop (smallest f-number) I can use is F/3.3. While at 80mm the largest (smallest f-number) F-stop I can use is 5.6. In this example, zooming in allows less light to pass through compared to shooting the same scene at the widest possible angle on the lens. However, prime (fixed focal length) lenses have only 1 f-stop number on the lens. There are certain situations where you would want to use a smaller f-stop vs. a larger f-stop. These issues will be discussed later in the article.

Now that we know that a smaller f-stop number = more light, and a larger f-stop number = less light, how much does each stop actually affect the light? Each f-stop in the series above lets in twice as much or the number below lets in half as much. For example, f/2.8 lets in twice as much light as f/4. Again, the smaller number means more light (twice as much light as the stop below it). An f-stop of f/5.6 lets in half as much light as f/4. This isn’t really that important to remember, I don’t want to confuse you with too much information that’s not really relevant, but just remember the main concept of “the smaller the number, the more light” is the important idea here.

The aperture is controlled either by the camera (calculated due to the amount of light in the picture you are trying to take) or the photographer (manually twisting the aperture ring or by twisting the dial on the back of the camera body) to set the aperture. If the photographer is manually setting the aperture by turning the aperture ring on the lens, he/she can feel the ring ‘click’ with each turn. This is opening or closing the aperture, depending on which way you turn the ring. If the photographer changes the aperture by the dial on the back of the camera, which most modern lenses use, he/she can feel a click with each turn of the dial.

Now that you have a better understanding of what the aperture is and looks like, why is it important and how does it affect exposure?

Aperture is part of the Big 3, or “Exposure Triangle” if you will. There are 3 main components of determining the exposure of any particular image. These components are aperture, shutter speed, and ISO. The combination of these 3 components will determine if your picture comes out underexposed, overexposed, or “correctly” exposed. Why do I say “correctly” exposed with quotations marks? I simply say it this way because there is a difference between a technically correct exposure and a creatively correct exposure; however that is for another article.

So when would you want to use a small f-stop number (remember this means that MORE light can come through) as opposed to a large f-stop number (reducing the amount of light able to pass through)? Well it really depends on what you’re shooting. The aperture basically determines how large your depth of field (the zone of apparent focus) is.

• If you want those nice images that have the sharp subject contrasted against the out of focus background [image to the right] you would use a small f-stop number. The smaller the f-stop number (the more open you shoot) the shallower the depth of field will be in your image. These small f-stops help to make great portraits and isolation images of wildlife and people.
• If you’re shooting landscape images then you would most likely want to use a very large f-stop number, such as f/22. This will give you a greater depth of field, resulting in a sharper, image throughout the picture. For a more in-depth look into depth of field, head on over to the article, Understanding Depth of Field.

Here are a few terms that are good to know with reference to aperture.

• “Opening up” – Meaning you’re making the aperture opening larger, letting in more light and decreasing your depth of field zone.
• “Stopping down” – Just the opposite of opening up, you are closing the aperture to let in less light and increase your depth of field zone.
• “Wide open” – You can probably guess, it means you are shooting at the maximum (widest/smallest f-stop number) aperture that your lens can go to.
• “A fast lens” – This refers to the maximum aperture. If the lens has a maximum aperture of anything above (smaller than) f/2.8 it is considered a fast lens. Why? Well it is considered a fast lens because you can use a faster shutter speed since the lens allows more light to come in. (This is discussed more in the Understanding Exposure: Part 2 article).

To review, the aperture’s part in the big 3 in controlling exposure is by opening up or closing down the aperture blades, letting in more or less light. That should make sense.

The smaller the f-stop number, the more light can travel to the sensor or film. Just the opposite with a big f-stop number.

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