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What is Aperture?

In optics, an aperture is a hole or an opening through which light travels. In all modern lenses, we have a diaphragm placed in the optical path, which controls the size, the area of this opening.

Diaphragm on a 50mm lens. https://commons.wikimedia.org/w/index.php?curid=6268143

Diaphragm. Big or small aperture.


A diaphragm is a group of opaque blades mounted on a rotating mechanism. If this mechanism turns in one direction the blades are pushed toward the center of the lens. If it turns in the opposite direction the blades retract.

When the blades are pushed inward the opening inside the lens through which light travels is reduced. When the blades are retracted this opening widens until it reaches its maximum area. This area has the same diameter as the lens barrel and it can't grow larger for the physical limitations of the lens construction.

Aperture in Photography Definition. Aperture and Depth of Field.


Aperture in Photography is this opening, this hole through which light travels. When this opening called aperture gets smaller, two are the direct effects. First, less light reaches the film frame or the sensor. Second, the area of sharpness around the subject of our picture is increased.

Aperture on camera is directly involved in two critical concepts pertaining photography: exposure and depth of field.

Stopping down the lens. Aperture and shutter speed.


In the photographer's lingo, we say we "stop down" the lens when we close the diaphragm, therefore reducing the aperture of the lens. In combination with shutter speed & ISO number, the aperture size will regulate the film's or image sensor's degree of exposure to light.

Camera Mode: Aperture Priority. Aperture examples.


The camera mode that goes by the letter A is the mode that lets the photographer control Aperture. In this mode, the photographer picks the Aperture setting and the camera, after metering, sets the Shutter Speed and the ISO Number.


#aperture #photography #photographers

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