What is Photography?

Photography is derived from the Greek term of phos graphis or “painting with light”. From the simplest pocket camera to the most modern digital SLR cameras in the market today, all cameras function as an image capturing device by harnessing different spectrum of light to create an image.

While different people have different reasons for starting photography, photography fundamentals remain constant and apply to all subject matter and intentions.

The challenge of photography lies in trying to attempt to reproduce reality on a static, two-dimensional surface from an active, three-dimensional world. To be able to convey emotions, relive memories, and stimulate imagination on screen or a piece of paper is an art by itself.

Armed with the knowledge of photography fundamentals will allow anyone to have a better chance of translating their vision into a photographic reality the way it was intended by the artist.

Content of this tutorial:

• How is an image captured?
• Shutter speed
• Aperture size
• Depth of Field
• ISO sensitivity
• ISO Noise
• So what settings should I use?

How is an image captured?

In the most basic form, a camera functions like our eye. Light enters our eye and the eye renders an image through our optic nerves that transmits the different color information for our brain to decode and registers as an image.

In a digital SLR, the basic image capture follows the following sequence. Light enters through the lens which controls the amount of light through the aperture blades, then the light hits the shutter, then the subsequent light is recorded by the camera’s sensor (refer to Fig. 1).

Different types of cameras may have various lens, sensor, and processor variances, but they all function on the same basic premise.

In most cases, the end user has little control over how the camera processes and develops the image within the camera, but the photographer can control how the light is being harnessed before the image is registered in the camera.

The art of capturing light revolves around three photography fundamentals of shutter speed, aperture size, and ISO sensitivity. All three combined gives us an “exposure”.

Figure 2 illustrates a simplified analogy of how an exposure is made by using a faucet as a shutter, the nozzle of the faucet as the aperture, a pail as the ISO sensitivity, and the collected water as the exposure itself.

Shutter Speed

Selecting a shutter speed means instructing the camera how long the shutter remains open to capture light. The longer the shutter remains open, the more light registers on the camera’s sensor. Conversely, the shorter the shutter stays open, the less light registers on the sensor as well.

Referring to our faucet-pail analogy, opening the faucet valve for 10 seconds would yield more water in the pail compared to opening the faucet valve for 2 seconds. The same concept applies to shutter speed, the shorter the shutter speed, the less light is captured, and vice-versa.

So when do we use a fast or slow shutter speed? Like most things in photography, there are no hard and set rules when selecting an appropriate shutter speed as it will all depend on what the scene dictates and how you want the image to look. We can simply classify shutter speeds into two types, fast and slow.

Fast shutter speeds generally mean shutter speeds that can freeze motion, while slow shutter speed can depict motion from the subject. This, of course, depends on whether the subject is moving or not, and how fast the subject is moving in reality.

Fast shutter speed is usually used to stop motion. Freezing subjects like a car passing by, a child running, a bird taking flight, and so forth. The quick shutter action records an image in a fraction of a second, creating a sharp, motion-stopping image.

Using a fast shutter speed will usually result to sharp, detailed, and well defined edges in a photograph.

If using a fast shutter speed gives us sharp images, why not use this all the time? The answer is simple, going back to our faucet analogy, if you turn off the faucet quickly, the pail will not be filled in that short amount of time, and the result would be an unfilled pail. In camera term, we will have an underexposed, dark image as the sensor wasn’t able to receive enough light to render a clear image.

We need to slow down the shutter speed to allow the sensor to record more light to obtain a proper exposure.

If we slow down the shutter speed too much, the result would be an overexposed photo.

Slow shutter speed delivers more light onto a camera’s sensor and therefore is ideal when the scene doesn’t have a lot of light available or if you want to induce motion of a moving subject.

As long as the subject (and camera) is stationary, a still subject will remain sharp and well defined, as if captured by a fast shutter speed. However, when photographing a moving subject such as a fast car, a raging river, rush hour commotion, it is usually preferred to illustrate motion rather than freezing the action as the viewer will have a sense of action when looking at the photograph.

Opposite of a fast shutter speed’s intent, using slow shutter speed will not be able to freeze a subject’s motion, however. If your intent is to freeze a dancer’s performance, for example, using a slow shutter speed will cause the subject to be blurred. The same thing happens if you try using a slow shutter speed if the camera is not stable, your image will be blurry.

To summarize, a fast shutter speed freezes motion while a slow shutter speed allows motion to be recorded as a blur.

In order to find out how fast or slow our shutter speed has to be, we have to understand how aperture works as well.

Aperture size

The aperture size dictates how large the opening of the lens’ aperture blades can open to in relation to the focal length of the lens. The larger the aperture opening, the more light passes through the lens, and the smaller the aperture size, the less light passes through the lens.

Returning to our faucet analogy, we’ve determined that the shutter speed is the amount of time the faucet valve is left open. We can alter the flow of water by introducing the aperture size into the equation. The aperture is represented by the diameter of the faucet nozzle.

If the faucet’s spout diameter is enlarged, more water will flow through the faucet and the pail will be filled up at a faster rate. Conversely, the smaller the diameter of the faucet’s spout the longer it takes for the pail to be filled with water. That’s exactly how aperture settings work, if the shutter speed is constant, altering the aperture size will increase or decrease the amount of light for the exposure.

Depth of Field

In addition to controlling the amount of light, changing the aperture also alters the depth of field of an image. To put it simply, depth of field (DOF) means the area of acceptable sharpness. Within an image there are areas of the image that are sharp and areas that fall out of focus, adjusting the DOF will allow you to choose how much (or how little) areas to be kept in focus in your image.

By using a large aperture opening (usually designated by a low f/ number on your LCD), the DOF is narrower. This is also called selective focus as only partial areas of your image will be in focus. Any areas in front and behind the DOF will not be sharp and will be blurry.

By using a small aperture opening (designated by a larger numerical f value on your LCD), the DOF is wider, allowing more of the scene to remain within the area of focus.

ISO Sensitivity

Last piece of our exposure puzzle is the ISO rating of our camera’s sensor. ISO sensitivity dictates how “sensitive” the camera’s sensor is to light. The more sensitive it is to light, the less amount of light it requires to make an exposure, and vice-versa. The sensitivity rating is indicated by the ISO setting of our digital SLR.

Returning to our faucet analogy again, the ISO is now represented by the pail itself. The smaller the pail (high ISO), the faster it is to fill and vice-versa

If our shutter speed (faucet valve’s opening) and our aperture (diameter of the faucet) are constant, the size of the pail will alter our final outcome.

Let’s say we have a 5 gallon pail that takes 5 seconds to fill up, without altering the shutter speed and aperture values (valve opening and faucet size) increasing our ISO (smaller pail size) will now require less than 5 seconds to fill up. On the other hand, decreasing our ISO (larger pail size) will now require more than 5 seconds to fill-up.

It would seem that using higher ISO would be more ideal as it would entail shorter exposure times to create an image. Increasing ISO sensitivity, however, has a drawback, as the sensitivity increases, so will digital noise and image quality deterioration.

ISO Noise

ISO noise appears as random colored dots and smudges in an image that deteriorates the details of a captured image.

The advancement in sensor and processor designs in most modern cameras have minimized the negative effects of high ISO noise, but the image quality of an image captured with low ISO setting will always be superior as it contains the most amount of image data and least amount of noise.

The decision to select an appropriate ISO setting would highly depend on the purpose and viewing size of the captured image. Most newsprint, web sharing, and small prints do not require maximum details for their images, so higher ISO settings would be ideal when capturing high speed action. Fine art, wedding albums, and large print ads will require noise-free images as much as possible to retain maximum detail and image quality, so low ISO settings are required.

So What Settings Should I Use?

As a photographer, experience will allow you to maximize the combination of these three settings (shutter speed, aperture size, and ISO) based on your desired and required output.

To better understand how each setting affects and image, it would be best to practice as much as you can with repeatable subjects such as items and scenes you can find in your home or neighborhood.

Understanding how shutter speed, aperture size, and ISO change the final image with the same subject will undoubtedly fast-track your understanding to proper exposure.

We will learn how different combination of shutter speed, aperture size, and ISO settings affect a photograph in our next article. Stay tuned!

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