Nov 24 2009

Basic Exposure Techniques

Published by at 9:58 pm under General

 

Lighting plays the major role in the photographing process. No matter how good is your composition, if the lighting is not good, then the whole photo will not be good either. It has this power to ruin a good image and make it useless, but it also has the power to make an ordinary photo, a great work of art. Learning how to capture the correct amount of light is an essential part of photography.

During the capture of a single photograph, the photographic medium (film or digital sensor) is allowed to gather a certain amount of light indicated by its exposure. There is no fixed value of a correct amount of light, because it depends on the available lights, the objects, and the photographer’s judgment. But there is a range of accepted exposures that, while produce different results, cannot be seen as mistakes. Unaccepted exposures are, in general, due to a mistake rather than a photographer’s intention.

Low lighting conditions require high exposures to allow more light into the sensor, brightening up the final photograph. Otherwise, the photograph will be underexposed, having too many dark areas, the dark objects loosing their details, and the bright objects becoming dull. Alternatively, a bright scene will need short exposures, limiting the amount of light collected by the sensor, yielding a well exposed photograph. If more exposure is used, the photograph will become too bright with many blown highlights.

Exposure relies on two factors: shutter speed (exposure time) and aperture. Shutter speed controls the time for which the shutter will stay open. Slow shutter speed means more exposure, while fast speed will allow less exposure. As for aperture, it determines how wide the lens is opened. Narrow aperture will let less light pass through it than a wide aperture. Another component that affects exposure is the ISO speed, which indicates the light sensitivity of the sensor. At high speeds, the camera will collect light faster and will amplify the sensitivity of the sensor, but will add noise to the photo.

When manually setting the exposure, the photographer usually sets the aperture and the shutter speed independently. As for automatic exposure settings, the camera will determine the degree of exposure needed according to the light metering technique used. Exposure compensation is a method of adjusting the exposure by adding fixed exposure values, which is also very useful for camera owners who don’t have manual exposure settings.

In case of extreme lighting conditions, it will be difficult to all cameras (including DSLRs) to get acceptable exposure for all shadows and highlights. Usually, photographers take the same photograph at different exposures, and combine them together using software programs.

A good approach to learn more about exposure is to look at the exposure settings of your previous photographs, and compare them Look for the exposure time (shutter speed), the aperture, the ISO speed, and the exposure compensation in the data that is stored in your image files. As a result, you will get a clearer idea on how exposure can impact your photos.

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