What is Aperture in photography?
Shutter works in the DSLR camera as an eyelid to block the light (External link). In the same way, Aperture works as a pupil of the human eye. The pupil determines the value, how much light it should allow into the retina. Value of aperture in photography holds the same importance. Aperture is embedded in the camera lens. Aperture is made up by several blades stacking together. It opens diagonally to let the light in.
Aperture and Light:
The opening and closing mechanism of the aperture is controlled by camera body. Aperture is defined by f/stop numbers like 1.4, 1.8, 2.8, 3.5 and so on. It works appositely in relation to numbers. Highest f/stop number narrows the aperture ring having a tiny hole to pass the light through it. Lowest f/stop number like f/1.8 passes more light through the hole.
Aperture and Shutter:
Aperture and shutter helps together to expose the photo correctly. Both let the light enter into the camera. But there is a difference in nature of their functions. Shutter controls the light based on a fraction of second. It is more related to the time and speed of light.
But aperture controls the amount of light from the source based on its f/stop numbers. You can decide the amount of light to expose your photos by playing with f/stop numbers. Smallest value like f/1.8 widens the blades and more light comes in. If the shutter speed is slow like 1/25th of a second, sensor will get more time to absorb the light. This will make the photo extra brighter (over-exposed). Slow shutter speed works well with wide aperture hole, in case, the light coming from the source (bulb or sun) is not enough.
You can use wide aperture with fast shutter speed in a well-lit environment. In case the fast shutter speed still overexposes your shots, use high aperture value like f/8 or f/11. High f/stop number will narrow the hole of the aperture ring. There are no thumb rules for using the specific f/stop number with shutter speeds. One can learn it by continuous experimenting.
Aperture And Depth of Field (DOF):
Depth of field is a distance from the foreground to the background. Aperture helps to single out the subjects within a depth of the scene. As I mentioned above, aperture acts like a pupil of a human eye. Try widening your pupil against a light source. Source of the light will turn blurry.
Exactly, how wider the aperture opens, the more light sources get blurry based on the distance. Smallest aperture value like f/1.8 or f/2.8 will blur the background more. This blurry or de-focused background is known as shallow or small depth of field.
Aperture And Bokeh:
Aperture controls the light which comes through the sources like bulb, sun or small holes. The smallest f/stop value turns these light source blurry in round shapes.
Shapes of the bokeh depends upon the shape of the aperture ring. There used to be different shapes of bokeh in the past. There are still some manufacturers who design different shapes of aperture plates.
These blurry shapes are bokeh. It makes photos stunning and brings wow results. Wider opening of aperture creates more bokeh out of light source. It is appealing to such an extent that photographers try to add bokeh to the background purposely.
Aperture And Fast lens:
Lens manufactures design different lenses for specific purposes. Aperture and shutter goes hand in hand. The wider aperture opens up the possibility to use fast shutter speed. The lens with the smallest value of aperture like f/1.4 or f/1.8 or f/2.8 works faster. Not every lens comes with such smallest aperture value.
Smallest value of aperture helps the lens to pass the more light into the sensor. If your lens has smallest aperture value of f/4, you may have difficulty to shoot in low light conditions. Fast lenses work extra-ordinary under low light situations. That is why, Professional photographers have special love for fast lenses. Their kit is full of such pro lenses. These lenses bring more stunning results than other normal lenses. Generally, fast lenses are expensive.
Read also: How DSLR Camera Focuses?
Post has been written for the beginners. Many broader technical details/jargons have been left out purposely to avoid the confusion for them. Feel free to ask for more suggestions through comment box.