Understanding Photography: Aperture, ISO and Shutter Speed


If you have a photographer friend then words like aperture, ISO and shutter speed must sound familiar to you. For non-photographers these words seems like some rocket science but in reality these three words are like the three pillars of the photography.

What is Aperture?

Always wondered how the background is blurred or how everything comes into a focus in a photograph then you really need to know about the magic of aperture. In simple words, aperture is an opening, hole or gap. Similarly in photography aperture is a hole within a lens, through which light travels into the body of the camera. Every camera is designed like an eye of a human being.  The function of an aperture in camera is similar to the function of a pupil in an eye. Larger the pupil the more light, the more light enters into the retina and in a same way large aperture means more light entering into the camera. In photography, aperture is described in f-numbers. A smaller f means a large aperture while a larger f means a small aperture. f/2.0 is larger than f/8.0.

A larger aperture such as f/32 will bring everything in focus while a small aperture let’s say f/1.4 will make the foreground objects sharper and will background objects look blurry.


What is ISO?

ISO simply means the level of sensitivity a camera have. ISO is one of the most important and most expensive part of a camera which is responsible for collecting the light and transforming it into the final image. With a higher ISO you can capture images in low-lights without the use of a flash. However higher ISO is not desirable as it adds grain, or popularly know as noise, to the picture. Every camera has a lowest ISO number which produces highest image quality. ISO Speed varies from ISO 100 to ISO 3200. Now the question arises what is the difference between ISO 100 and ISO 3200. Speed!

ISO 3200 can capture an image in sixteen times less than ISO 100.


When to use low ISO and when to use high ISO?

When there is plenty of light, or the camera is mounted on a tripod, in these cases low ISO is desirable.  High ISO can be used for indoor photography and in cases where you want to get ultrafast shot like shooting birds.

Always try to use base ISO (ISO 100 or ISO 200) to get highest image quality. If you are comfortable with noises in your image you can go for higher ISO.

What is Shutter Speed?

Before understanding what shutter speed is, you should know about Camera shutter. In simple words, camera shutter is like a curtain in front of the camera sensor which remains close until the camera fires. As soon as camera fires, the shutter opens and exposes the camera sensor to the light passing through lens aperture.  After it, the shutter closes immediately thus preventing the light from hitting the sensor.

So now shutter speed or exposure speed is the time for which a camera shutter remains open to expose light. Fast shutter speed can help in completely freezing the action. Slow shutter speed makes the images looks blurry. Slow shutter speed is also used in landscape photography for creating a sense of motion. Thus shutter speed is used to create a blurry effect or sometimes motion effect in a photograph.



Aperture ISO Shutter Speed
Definition A hole within a lens. Sensitivity of a camera. Speed of camera shutter.
Function Allows to control the amount of light entering into the camera which is needed for the image. Used for transforming the light entering to the camera into an image. Controls the length of time for which camera shutter should remain open.
Unit f-numbers

f/2.0, f/8.0

ISO number

ISO 100, ISO 200

Fraction of seconds

¼, 1/250, 1/4000

When to use high To focus on everything in the image. For indoor photography and for fast moving objects. For creating a motion effect in an image.
When to use low To focus on foreground objects only and for making background images blurry. In plenty of light or when camera is mounted on a tripod. For creating a blurry effect in an image.


Now you don’t need to look like an idiot when your photographer friend talks about these terms. Just advise him what you have learned from this post.

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