Aperture is a recurring setting in the composition of my photographs. I always use the aperture priority of my camera. Speed does not matter for the subjects I photograph and this is even more true since the cameras are able to get into high ISO.

On most analog cameras of the 80s, the aperture values are accessible via the rotating ring belonging to the attached lens. This is still true today digital cameras FUJIFILM X. On the housings modern DSLRs, the lens is now very often devoid of an aperture ring. Just refer to the documentation included with the device to locate the adjustment control of the diaphragm. Ergonomically designed for NIKON D7000 as the aperture is displayed on the top LCD panel and can be changed according to diametrically opposed knobs to trigger.

This rotating wheel acts on aperture of a key element in camera body : Iris. This is nothing more than a circular section, placed before the window is opened more or less, to control the amount of light that will be able to reach the film or sensor. This component is a thin sheet of metal or cotton, very delicate, it is better not to touch, as fragile as the shutter, although it is more difficult to reach because located inside the lens.

Depth of field

Insulating aperture

We can make several successful shots of the same subject at different apertures since the shutter speed is recalculated according to proper exposure. A still subject to the horizon or on the focal plane, the differences will be very sensitive but on a subject on a different plane, the choice of the aperture becomes a determining factor. It is found in the context of using a large aperture (less than or equal to f/8) that only the subject is in focus and the background is blurred. In contrast, the use of a smaller aperture (larger than or equal to f/16) provides a uniform sharpness over the entire image. This is simply the phenomenon manifestation that is commonly called depth of field.

Aperture lower than f/8 (Picture A) ; Aperture larger than f/16 (Picture B)

A device is set to infinity and diaphragm to its largest aperture, the sharpness will be the maximum for an object at infinity and still sufficient even on a closer shot. This depth of field limit is the hyperfocal distance. It is calculated using the formula : H = (F x e) / f - F being the focal length ; f the relative openness ; e tolerance sharpness expressed as a fraction of the focal length. Just fun to gradually close the diaphragm to gradually see the depth of field to expand and see the nearest become net objects, one after the other. A 50 mm lens at f / 16 allows the pictures production with depth of field maximum : All objects are sharp.

For a very emotional photography, never underestimate the power of an insulating aperture for any subject (flora or portrait in these examples). In heavily opening the diaphragm (the smallest possible values of the lens used to f/8), you will get an insulation of the main subject relative to a foreground and/or a deliciously blurred background. The dosage of the blur intensity arising from the selected aperture.

Copyright Bryan F.Peterson

Copyright Arnaud Fiocret





Since 1997


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