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Brian Tobey



From the time it was invented, people have always been intrigued by photography, to capture images for memories, art, science, or just for fun. Digital photography and the web have made it even easier to capture photographs and share them, than ever before. Yet the basic concept of photography has not changed. This is an important concept to grasp, as camera vendors and marketing push newer cameras, with new features and advanced electronics. It turns out that electronics have less to do with photography than optics and physics.


In this age of digital photography, some cameras do not even provide the ability to change important controls such as aperture and shutter speed. Instead they push auto modes and scene modes that do everything for you. That works great for those who are just looking to capture something quick. But photography is much more than that. In art, it’s more about personal expression, while in science and product photography, its more about accuracy and precision. It is important to have the controls available to adjust exposure, white balance, color accuracy, and ISO.

This website focuses more on DSLRs and mirrorless cameras. These cameras provide the controls necessary to fulfill almost all aspects of photography.


Focal length is the magnification of a lens. The magnification amount for a given focal length also depends on the image sensor or film size. The focal length is a measurement of the distance between the rear nodal point of the lens to the image sensor, when the lens is focused at infinity.

Zoom lenses provide the ability to change the focal length. These are the most flexible, because you can vary the focal length depending on the particular shot. However, there are drawbacks to zoom lenses, not just in image quality, but in aperture ranges. Prime lenses or fixed focal length lenses do not zoom, but can provide excellent optics and greater aperture ranges.


Aperture is the iris of the lens. It opens and closes depending on the f-number. It determines how much light enters the camera for a given shutter speed. Low f numbers, like f/1.4 allow a lot of light in, while higher f numbers, f/16, allow less light. The higher f-numbers provide greater depth of field, permitting a greater distance to be in focus. The opposite is true for lower f-numbers, which have less depth of field. Depth of field is actually quite complicated and there is a lot more to it than just f-numbers. You can read more on depth of field.

The f numbers, or stops, are based on powers of 2. It starts at f/1 which is 2 to the power of 0/2, which is 1. The next stop is f/1.4 or 2 to the power of ½, which is the same as the square root of 2, which is 1.41 or f/1.4. The next stop is f/2, or 2 to the power of 2/2, which is the same as 2 to the power of 1, which is 2, so the next stop is f/2. This goes on and on. It is better described in the image below.

Different lenses are designed with different minimum and maximum apertures. Lenses are usually titled based on their focal length and maximum aperture. Note that the maximum aperture is the minimum f-number. They are inversely labeled. Lenses with large apertures, or small f-numbers, usually cost more because more glass is required to render more light. Also, zoom lenses are complicated and usually have higher f-numbers. Prime, or fixed focal length lenses, can have larger apertures and allow more light than zooms.


The shutter is the device that opens and closes inside the camera for each picture. It is normally closed, allowing no light to enter the camera. When the shutter button is pressed, the shutter opens for a specified time, and then closes. Together both, aperture and the shutter speed control the exposure of an image.

The shutter speed also controls the ability to freeze an image. Depending on the shot, shutter speeds of 1/2000th of a second are required to freeze sports action, while slower shutter speeds, like 2 secs, are sometimes used to show motion and blur waterfalls.


ISO controls the sensitivity of the camera’s image sensor. It is pronounced eye-es-oh. In low light situations, shooting at higher ISOs increases the sensitivity of the sensor so you can shoot at higher shutter speeds and avoid blur. However, higher ISO sensitivities add noise or grain to an image. Conversely, lower ISOs require a longer shutter speed and a longer collection of photons are acquired for higher quality image. ISO is the reason why images indoors can look grainy when shot in auto mode. Auto mode cranks up the ISO to prevent blurring in dim light and consequently adds noise to the image.

[Read more on ISO Sensitivity]


White balance controls the overall color cast of an image. Not all lights are the same, and some produce more green or red or blue. For example, incandescent lights produce more yellowish red light, and fluorescents produce more greenish light. Our brain compensates this when we perceive this with our eyes.

Adjusting white balance compensates for the various colors that different lights produce. Sunlight is typically the most balanced and easiest to compensate for. Cameras provide the ability to adjust for white balance using presets or by calibrating the white balance.

[Read more on White Balance]


ISO Sensitivity | White Balance | Composition