Understanding Aperture and Depth of Field (DOF) in Photography

Hello friends!

Lights of Diwali

Since last 2 posts I’ve been explaining you about exposure and how to get rid of auto mode. One thing always remember that keep experimenting with different settings and modes. More you experiment with your camera, more you’ll learn about exposure. Day by day you’ll come to know that there are tremendous possibilities and vast creativity you can make. It may also be possible that you find your own way, your own type of photography, a new path on which no one has ever walked. But hard work is always the key! Let us move towards the Aperture. Learning the aperture is learning the creativity. Once you get your hands on this king, you’ll come t know that creativity in photography is endless, just like any other art!

What is the Aperture?

Aperture is the size of opening in the lens while picture is being taken. The Aperture controls the lens’ diaphragm, which controls the amount of light travelling through the lens. You must have seen, when shutter release button is clicked, diaphragm in the lens opens for a small amount of time. Size of this opening is controlled by the aperture value. Bigger is the size of opening, more is the amount of light passed through the lens and brighter will be the image.

Aperture value displayed as F22

Aperture value displayed as F22

Aperture is measured in “f-stop”. You must have seen values like f/1.8, f/3.5, f/12 in EXIF details of an image or on camera screen (on camera display it shows like F2, F11, etc). this f-stop value indicates size of the opening in lens while shutter release button is hit. But here, don’t go directly on the values because they are not what they look like. Amateur photographers think that smaller the value in f-stop, smaller will be the opening. But it is exactly opposite. smaller the value of f-stop, bigger is the opening of diaphragm, i.e, opening for f/1.8 is much bigger than opening for f/11. It is illustrated by following image.


Aperture range


Now it is obvious that image will also be much brighter for f/1.8 than for f/11. Also if you are changing aperture, shutter speed and ISO should also be changed if exposure value is to be kept same. But changing the value of aperture also changes one most important factor in photography, which is “Depth of Field”.

Depth Of Field (DOF)

macro photo of a rose

Macro photography of a rose


Impact of any image depends on the depth of the image. Some images require more depth, some require less, depending on the scene. Technically depth of field refers to the range of distance that appears acceptably sharp, or it is that amount of your shot that will be in focus. In various images you may have seen that particular part of image is quite sharp, but portion in front of and behind the sharp portion is blurred. One can say that the length or size of that sharper portion is the DOF of the image. Large depth of field means that most of your image will be in focus. Small (or shallow) depth of field means that only part of the image will be in focus and the rest will be fuzzy or blurred.

Depth of Field explained

Depth of Field explained

Now how to decide DOF? Your aperture value also controls the DOF. smaller f-stop or aperture value gives you smaller or shallow DOF. While larger value of DOF means large DOF. Reason for this behaviour lies in physics and optics, if you want to know in brief, you can google it! Deciding DOF depends upon your scene or subject of photograph. here are few general examples:

1. To capture landscapes, we need to cover whole area in the scene. So it is recommended that large DOF should be used.

2. In portraits, we usually focus on the subject we want to capture. So DOF is kept smaller with focus on subject. Also blurred background creates wonderful bokeh in image.

3. Similarly in macro photography, subject should be in focus. thus to eliminate remaining portion, DOF is kept smaller.

Landscape photo at Rohatand pass, Himachal Pradesh. Larger DOF is used

A landscape photo of Rohatand pass, Himachal Pradesh. Larger DOF is used.

Macro photo of an eye. DOF is kept smaller

Macro photography of an eye. DOF is kept smaller

Portrait of statue of Buddha at Manali.

Portrait of statue of Buddha at Manali.

And there are many other examples. But it is not necessary that you should always follow these measures. By combining aperture with shutter speed, you put into your grasp real creative control over your camera. Aperture or DOF is where lots of magic can happen in photography. Each combination gives something new and amazing. So keep on trying something new, but meaningful, of course!

Leave a Comment

* : 16 + 4 =