Aperture

Aperture

Aperture being one of the three main elements in photography while other two being shutter speed and ISO, it can be used to control the overall exposure. Aperture determines the amount of light entering to the camera by varying the diameter of the iris. For example if the iris is wider, more light can go through to the camera and if the iris is narrower, relatively small amount of light can go through.

   Figure 1.0 lens with high and low aperture

The F-Stop value (Measurement of Aperture)

Stop value in photography act as a measurement of exposure and will depend on the 3 major elements aperture, shutter speed and ISO. When it comes to aperture, it is denoted as f-stop. With the f-stop value you can determine the depth of the field. In lower f-stops, amount of light can pass through from the lens is high and pictures appear to be blurry this is called a shallow depth of field and this lowers the clarity of the entire picture. A high f-stop picture is less blurry and has higher number of focal points and so it is a picture with a higher depth of field.

Figure 2.0 f-stops and aperture.

How Aperture Determines the Depth of Field

Aperture directly involves in depth of field which is in focused objects in a photograph. For example if the f-stop is high as f/32 then all the objects in the photograph will appear focused, and if the f-stop value is low like f/1.4 then the focused objects will appear sharp but background objects will appear blurry. A single photograph means series of layers capturing at once. Depending on these layers, the depth of the photograph can be visualized.

                                                               

 

Figure 3.0 Low f-stop photograph and a high f-stop photograph

In figure 3.0 we can see that photograph on the left has most layers blurred out and only the object in-front appears to be sharp. This is known as a shallow depth of field because the background of the image cannot be visualized.

The photo on the right has more layers focused and sharp so the details of the each layer are clearer. This can be identified as an image with a higher depth of field.

How Aperture Controls the Bokeh effect

The term 'Bokeh' comes from the Japanese word 'boke' which means blurry. The effect of Bokeh is considered to be the soft blurry background that you achieve when capturing a subject. For a good Bokeh photograph, your lens should be set in high aperture position and focus on an object, Bokeh is highly dependent on the aperture, so in order to obtain more Bokeh effect out of the 

picture you need to have high aperture lens. For instance f2.8-f4.0 lens can give you a reasonable Bokeh effect, but for a good quality blurry background or Bokeh you may need f2.8 or higher lens.

Figure 4.0 Bokeh example

As you already noticed both the pictures in figure 4.0 are with shallow depth of fields and only few layers appear out as sharp so both these pictures were taken at higher aperture levels, hence the background is blurred.

Picture on the left has Bokeh lights which happen to be the shape of the lens iris when it is widely opened.

How to Use Aperture in Photography

Since we already know what aperture is and how to control it, it is time to see when and where to use it. We can use shallow depth of field to focus and direct the lenses in to a particular subject and this is useful in object photography and portraits. If you are taking a landscape or a scenery, in most of the cases you need all the layers sharp in other words a deep depth of field. So when taking these kind of pictures it is better to use small apertures (higher f-stop).

Lighting conditions are also affected by aperture, if the lighting conditions are very good as in mid-day you can lower the lens aperture allowing only small amount of light to go through the lens and take pictures without being over exposed. Similarly in low light conditions such as at dawn or at night you can use high apertures to get more light into the camera and avoid being under exposed.

Actually, when controlling aperture levels, there are no limitations and boundaries. It is always up to your imagination and therefor based on the picture you take you can control the aperture level accordingly.