You can adjust the aperture setting and shutter speed
to create several different correctly exposed images. The relationship
between the aperture and shutter is known as reciprocity. Reciprocity
gives the photographer control over the depth of field of the image,
which controls the area of the image that remains in focus. This is the
easiest way to control what part of the image you want the viewer to pay
attention to.
For example, opening the lens aperture by one stop and decreasing the shutter speed by one stop results in the same exposure. Closing the aperture by one stop and increasing the shutter speed by one stop achieves the same exposure as well.
Therefore, f4 at 1/90 of a second is equal to f5.6 at 1/45 of a second. The reason is that the camera’s aperture setting and shutter speed combine to create the correct exposure of an image.
I have read this lovely Article in one of the help documents for Aperture !!!
For example, opening the lens aperture by one stop and decreasing the shutter speed by one stop results in the same exposure. Closing the aperture by one stop and increasing the shutter speed by one stop achieves the same exposure as well.
Therefore, f4 at 1/90 of a second is equal to f5.6 at 1/45 of a second. The reason is that the camera’s aperture setting and shutter speed combine to create the correct exposure of an image.
I have read this lovely Article in one of the help documents for Aperture !!!
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