Now that we know some of the basic controls available on your camera, let's try and understand how they relate to each other.
A correctly exposed image can be made using several combinations of aperture and shutter speed. The relationship between the aperture and shutter speed that enables us to vary the settings and still maintain the same exposure level is called reciprocity. Each combination results in the same level of exposure but the aesthetics on the image will vary a great deal (we'll talk about these differences in much greater detail in future posts).
Here's how reciprocity works.
Both aperture and shutter speed have the ability to increase or decrease the amount of light hitting the sensor, albeit in different ways (aperture controls the amount of light entering the camera, and shutter controls the duration). By using one control to increase the amount of light entering the camera and the other to decrease the amount of light by the same amount we can create an image that has the same exposure level but a different aesthetic.
Here's an example. A scene has been metered to provide a balanced exposure with the following settings: f/5.6 and 1/100. Now if we wanted to increase the depth of field and still maintain the exposure level we can narrow the aperture by one f-stop (f/5.6 to f/8.0) and slow the shutter speed by one f-stop (1/100 to 1/50). If you wanted to decrease the depth of field you would widen the aperture by one f-stop (f/5.6 to f/4.0) and speed up the shutter speed by one f-stop (1/100 to 1/200). All of these changes assume that the ISO value stays the same.
And finally a few samples to demonstrate the concept. The four images below were shot using different combinations of aperture and shutter speeds but reciprocity was maintained. Clearly the exposure level is identical in all images but a closer look will show subtle differences in the aesthetic caused as result of the particular aperture and/or shutter speed.
Hint: look at the cup that's further away in the image and notice how it goes from being slightly blurred to sharply in focus.
A correctly exposed image can be made using several combinations of aperture and shutter speed. The relationship between the aperture and shutter speed that enables us to vary the settings and still maintain the same exposure level is called reciprocity. Each combination results in the same level of exposure but the aesthetics on the image will vary a great deal (we'll talk about these differences in much greater detail in future posts).
Here's how reciprocity works.
Both aperture and shutter speed have the ability to increase or decrease the amount of light hitting the sensor, albeit in different ways (aperture controls the amount of light entering the camera, and shutter controls the duration). By using one control to increase the amount of light entering the camera and the other to decrease the amount of light by the same amount we can create an image that has the same exposure level but a different aesthetic.
Here's an example. A scene has been metered to provide a balanced exposure with the following settings: f/5.6 and 1/100. Now if we wanted to increase the depth of field and still maintain the exposure level we can narrow the aperture by one f-stop (f/5.6 to f/8.0) and slow the shutter speed by one f-stop (1/100 to 1/50). If you wanted to decrease the depth of field you would widen the aperture by one f-stop (f/5.6 to f/4.0) and speed up the shutter speed by one f-stop (1/100 to 1/200). All of these changes assume that the ISO value stays the same.
And finally a few samples to demonstrate the concept. The four images below were shot using different combinations of aperture and shutter speeds but reciprocity was maintained. Clearly the exposure level is identical in all images but a closer look will show subtle differences in the aesthetic caused as result of the particular aperture and/or shutter speed.
Hint: look at the cup that's further away in the image and notice how it goes from being slightly blurred to sharply in focus.
Clicking on the images will take you to a higher resolution image on Flickr. Look under the 'Additional Settings' section for the shutter speed and aperture.
Until next time.
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