11-21-2016, Mobile Electronics -- In the last issue, Joey Knapp provided a detailed look at the composition portion of the photography presentation that he, (2016 Installer of the Year) Matt Schaffer and I presented at KnowledgeFest 2016 in Dallas, Texas. In this article, we are going to take a look at how a camera works and provide some insight into balancing shutter speed and aperture to create amazing images and different image effects.

The Digital SLR Camera

We are going to focus on an SLR (Single Lens Reflex) camera for this article. While you can certainly use a point-and-shoot or phone/tablet camera to take great photographs, there are occasions when you want more control over the image you are taking. A quick note on ‘what to buy’ if you are camera shopping. Once you take a picture, in most cases, you can never go back and capture that exact moment in time again. So capture the most resolution and detail you can. Shoot your photos in Raw format (if available) to capture more dynamic range (dark and light portions of the image). You can always throw away unnecessary information and resolution in Lightroom, but you can’t create it from nothing if you didn’t capture it. So, go big. You won’t be disappointed.

Taking a Photograph

A DSLR camera has an image sensor at the back of the body. The (interchangeable) lens focuses light coming from the object you want to photograph onto this sensor. When you look through the viewfinder to compose the image, light from the object is reflected upwards by a mirror into a five-sided glass prism that outputs the image to your eye.

When you press the shutter release, the mirror flips up and allows the light from the object to be passed to the image sensor. The pixels on the image sensor record the amount of red, green and blue light. That information is processed by the camera’s computer and stored on the memory card. If you are thinking to yourself “wow, that’s really simple,” then you are right. Taking a picture is simple.

Controlling Light

To capture an image, we need to ensure the image sensor on our camera stores the right amount of light information to accurately reproduce the image. Think of this like setting the gains on your amplifiers—you want to get loud, but not distort. We control the amount of light the sensor captures in two ways—by adjusting how long the mirror is held up, and by adjusting an opening in the lens.

How long the mirror is held up is called the exposure. This is measured in seconds. New cameras have exposure times that are adjustable from as fast as 1/8000 of a second up to ‘as long as you hold the shutter release’. Each step is a doubling or halving of the previous—so 1/4000, 1/2000, 1/1000, 1/500 and so on.

Controlling how much light passes through the lens is called adjusting the aperture. The aperture is controlled by a multi-element iris in the lens. The adjustment is called the f-stop. Each stop is a doubling or halving of area from one step to another. The stop number itself does not directly describe the amount of light coming through the lens. A large opening is a low number—some high quality lenses can open up as wide as f1.4 and close down as small as f22 or more. How wide the lens will open is often directly correlated to the cost of the lens.

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